Barking, Havering & Redbridge University Hospitals NHS Trust, Prenatal Screening Unit, Clinical Biochemistry Department, King George Hospital, Goodmayes IG3 8YB. UK
kevinspencer1@aol.com
Professor Spencer has a Hirsch Publications Index of 45 as of 2011. Professor Kevin Spencer is Consultant Biochemist and Clinical Lead in Biochemistry at BHRUT. He also is a Visiting Professor in Reproductive Biochemistry at King's College, London and Director of Biochemical Screening at the Fetal Medicine Foundation (London).
Abstract: To investigate the levels of placental growth factor (PlGF) in second trimester maternal serum in trisomy 21 cases and euploid controls - an unclear subject in the published literature.
Abstract: Background  The role of applied theatre in engaging both lay and professional publics with debate on health policy and practice is an emergent field. This paper discusses the development, production performance and discussion of 'Inside View'.(1) Objectives  The objectives were to produce applied theatre from research findings of a completed study on genetic prenatal screening, exploring the dilemmas for women and health professionals of prenatal genetic screening, and to engage audiences in debate and reflection on the dilemmas of prenatal genetic screening. Methods  'Inside View' was developed from a multidisciplinary research study through identification of emergent themes from qualitative interviews, and development of these by the writer, theatre producer and media technologist with input from the researchers. Findings  Inside View was performed in London and the Midlands to varied audiences with a panel discussion and evaluation post performance. The audiences were engaged in debate that was relevant to them professionally and personally. Knowledge translation through applied theatre is an effective tool for engaging the public but the impact subsequently is unclear. There are ethical issues of unexpected disclosure during discussion post performance and the process of transforming research findings into applied theatre requires time and trust within the multidisciplinary team as well as adequate resourcing.
Abstract: OBJECTIVE: To evaluate the role of PP13 as a marker for pre-eclampsia (PE) by comparing two different immunoassay platforms. METHODS: In this case-control study, first-trimester serum samples from 195 normal pregnancies and 37 pregnancies with PE were analysed for PP13 by using a manual DTL ELISA and the AutoDELFIA(®) platform. RESULTS: Levels of PP13 in first-trimester pregnancies increased with gestational age in controls and pre-eclampsia cases using both methods of analysis, but at different rates. PP13 levels were decreased in women with PE. Levels of the marker are found to be more reduced in PE cases when measured using the DTL ELISA compared to AutoDELFIA(®). CONCLUSION: Further studies are needed to compare the performance of the DTL ELISA and the AutoDELFIA(®) PP13 assays in terms of reproducibility, robustness and clinical performance in predicting pre-eclampsia.
Abstract: To determine the stability of first trimester free-β human chorionic gonadotrophin (free-β hCG) and pregnancy-associated plasma protein-A (PAPP-A) in dried blood spots (DBSs) under typical storage conditions.
Abstract: Placental growth factor (PlGF) is a proposed first-trimester screening marker for pre-eclampsia. This study investigates the stability of PlGF in serum and whole blood at typical routine storage temperatures.
Abstract: The Pregenesys Consensus Meeting held in Cambridge on 13 July 2009 was organized by the Pregenesys Consortium to review and critically discuss current knowledge regarding early markers of preeclampsia, to identify priorities and opportunities for future research, to consider issues that may need to be addressed in future recommendations and to highlight key issues in cost effectiveness and national policies concerning prediction and early screening for the risk of developing preeclampsia. This report summarizes the outcome of the Consensus Meeting and draws attention to issues for further investigation with specific regard to single versus multiple markers, early versus late risk identification, and the long-term effects on both maternal and perinatal health and the need to include these in any future cost-benefit assessment.
Abstract: To investigate the existence of a relationship between maternal body mass, maternal ethnicity and maternal smoking status and nuchal translucency (NT) in the first trimester of pregnancy.
Abstract: To measure maternal serum placental growth factor (PlGF) levels in trisomy 21 cases and controls in samples drawn before 11 weeks' gestation.
Abstract: To evaluate if levels of pregnancy-associated plasma protein-A (PAPP-A), free β-hCG and nuchal translucency (NT) used in first trimester aneuploidy screening and α-fetoprotein (AFP), unconjugated oestriol (UE3) and free β-hCG in the second trimester are altered in pregnancies with human immunodeficiency virus (HIV) infection.
Abstract: To investigate the role of placenta protein 13 (PP13) and pregnancy-associated plasma protein-A (PAPP-A) in hypertensive disorders and small for gestational age (SGA) during first trimester of pregnancy.
Abstract: To estimate the difference between levels of the two biochemical markers pregnancy-associated plasma protein-A (PAPP-A) and maternal serum free β-human chorionic gonadotropin (free β-hCG) in twin pregnancies relative to singleton pregnancies and establish an improved screening procedure for chromosomal abnormalities such as trisomy 21 in twin pregnancies.
Abstract: OBJECTIVE: To assess the impact of a vanishing twin on the levels of the biochemical markers used in the first trimester aneuploidy screening. METHODS: A retrospective analysis of free beta-hCG and PAPP-A levels in 270 women with a normal singleton fetus with ultrasound evidence of a vanishing twin pregnancy. Marker levels (as MoM) were compared in three groups-76 women with a second empty gestational sac, 194 women with a second gestational sac containing a dead fetus with a measurable crown rump length (CRL), and 1360 matched singleton pregnancies. RESULTS: In women with a second empty gestational sac, the median free beta-hCG and PAPP-A MoMs (0.968 and 1.040, respectively) were not significantly different from the 1.0 MoM in singleton pregnancies. In the group with a vanished twin with a measurable-CRL-there was a significantly increased median PAPP-A MoM (1.317) but the median free beta-hCG MoM was not changed (1.024). Modelling this bias in PAPP-A MoM the detection rate for trisomy 21 would fall from 85 to 75%. CONCLUSION: First trimester screening in the presence of a vanishing twin may lead to errors in risk estimation. In such circumstances it may be advisable to restrict screening to the use of nuchal translucency (NT) alone.
Abstract: OBJECTIVE: To determine maternal plasma levels of follistatin-related gene protein (FLRG) in the first trimester of pregnancy and assess its potential role as a marker for prenatal screening of Down syndrome. METHODS: Maternal plasma levels of FLRG were determined in 100 pregnant women with normal fetuses in their first trimester of pregnancy (i.e. 11th to 15th weeks). These results were compared with 20 cases with Down syndrome fetuses, taking into consideration clinical and demographic variables, such as maternal age, maternal weight, gestational age, smoking status and ethnicity. RESULTS: Maternal plasma median of FLRG in the normal population was 1.41 ng/mL with 95% confidence interval (CI) of 1.37-1.70 and interquartile range (IQR) of 0.88, during the 11th to 15th weeks of pregnancy. Maternal age and weight were the only variables significantly related to FLRG levels (p = 0.030 and 0.020, respectively). Only maternal and gestational ages were related to Down syndrome (p = 0.039 and 0.006, respectively). Maternal plasma levels of FLRG were not significantly different in the presence of Down syndrome fetuses compared to normal population (p = 0.63). CONCLUSION: FLRG can be successfully detected in maternal plasma in the first trimester of pregnancy. However, its levels are not significantly altered in the presence of Down syndrome fetuses.
Abstract: OBJECTIVE: To investigate first-trimester ADAM-12 levels in pregnancies which later develop hypertensive and growth complications. METHODS: First-trimester serum samples (11(+0) to 13(+6) weeks) were retrieved from frozen storage. 47 samples with at least one of the following adverse outcomes: pre-eclampsia (PE), small for gestational age, HELLP syndrome and gestational hypertension were analysed and 452 controls matched to the cases by gestational age and length of storage were analysed. ADAM-12 levels were measured by the automated AutoDELFIA immunoassay platform. RESULTS: ADAM-12 was found to increase with gestational age (11(+0) to 13(+6) weeks) and decrease with increasing maternal weight and in women who smoked. After correction, ADAM-12 median multiples of the median were increased in cases with HELLP syndrome, all PE and PE only. CONCLUSION: The increased first-trimester levels of ADAM-12 in PE and HELLP are in contrast with previous findings. The usefulness of ADAM-12 as a marker for adverse outcomes is still unclear.
Abstract: BACKGROUND: In this study we aim to investigate the stability of free-beta-hCG and PAPP-A over time in serum and whole blood in typical routine temperatures. METHODS: Serum pools were stored under the following temperatures: 30 degrees C, room temperature, refrigerator temperature and -20 degrees C, for up to 240 days. Stability of the markers in whole blood was examined in a shorter study and compared to serum. Samples were analysed using the AutoDELFIA and DELFIA Xpress analysers. RESULTS: On the AutoDELFIA, considering a 10% change acceptable, PAPP-A levels are stable in serum for 142 days at refrigerator temperature, 37 days at room temperature and 20 days at 30 degrees C. Free-beta hCG is stable in serum for 94 days at refrigerator temperature, 3 days at room temperature and 12 h at 30 degrees C. There was no significant change with either analyte after -20 degrees C storage for up to 240 days or after six repeated freeze-thaw cycles. In whole blood, free-beta hCG levels increased more rapidly compared to serum, especially at 30 degrees C. CONCLUSION: Normal handling of samples is only likely to minimally effect the risk assessment of chromosomal anomalies. However, careful attention should be paid to minimise the increase of free-beta hCG levels in samples shipped as whole blood.
Abstract: OBJECTIVE: To examine placental growth factor (PlGF) levels in first trimester maternal serum in trisomy 21 pregnancies and to investigate the potential value of PlGF in a first trimester screening test. METHODS: First trimester maternal serum from 70 trisomy 21 cases and 375 euploid controls were retrospectively analyzed for PlGF using a DELFIA Xpress immunoassay platform. Results were expressed as multiples of medians (MoM) for comparison. RESULTS: PlGF levels were significantly decreased in pregnancies with trisomy 21, 0.76 MoM versus 0.98 MoM in controls. Inclusion of PlGF into the first trimester combined test [maternal age, pregnancy associated plasma protein-A (PAPP-A), free-beta human chorionic gonadotrophin (beta-hCG) and nuchal translucency] would increase the detection rate by 0.5% at a 5% false positive rate. CONCLUSION: PlGF at 11 weeks to 13 weeks 6 days has the potential to be included as a marker for the detection of pregnancies with trisomy 21.
Abstract: BACKGROUND: Maternal serum placental protein 13 (PP13) has been proposed as a marker for prenatal screening of pre-eclampsia (PE) and other adverse pregnancy outcomes. This study aims to examine the stability of PP13 at different routine temperatures. METHODS: Maternal serum pools and whole blood samples were stored at '30 degrees C', room temperature or refrigerator temperature. Further, serum pools were also subjected to repeated freeze-thaw cycles. PP13 was measured at set time points using an AutoDELFIA research assay. RESULTS: Levels of PP13 are stable, defined as less than 10% change in concentration, in serum for 17.4 h at '30 degrees C', 3.4 days at room temperature and for at least 34 days at refrigerator temperature. PP13 concentration is not altered following three -20 degrees C to room temperature freeze-thaw cycles. PP13 is stable in whole blood for at least 3 days at all three temperatures studied. CONCLUSIONS: PP13 is a suitably stable molecule and can be treated under routine laboratory and normal transport temperatures.
Abstract: OBJECTIVE: The objective of this study was to examine first-trimester maternal serum placental growth factor (PlGF) levels in pregnancies which later develop hypertensive and growth complications. METHODS: In this case-control study, PlGF levels were measured by AutoDELFIA immunoassay platform. There were 47 cases of at least one of the following adverse outcomes: pre-eclampsia (PE), small for gestational age (SGA), haemolysis elevated liver enzymes and low platelets (HELLP) and gestational hypertension (GH) and 452 matched controls. RESULTS: PlGF levels were significantly lower in cases of all PE, early PE, HELLP, all SGA, early SGA and SGA without PE, but not in GH, late PE, late SGA, PE with SGA or PE without SGA or HELLP. CONCLUSION: Low levels of first-trimester PlGF provide a good indicator of SGA complications and some hypertensive disorders, in particular severe cases of PE such as early onset and HELLP syndrome.
Abstract: To evaluate the influence of maternal insulin-dependent diabetes mellitus (IDDM) on maternal serum free ß-hCG, pregnancy-associated plasma protein-A (PAPP-A) and fetal nuchal translucency (NT) thickness from 11 weeks to 13 weeks 6 days of gestation in a large cohort of women screened prospectively for chromosomal anomalies.
Abstract: OBJECTIVE: To assess the impact of early vaginal bleeding on the levels of markers used in first trimester screening for aneuploidy. METHODS: A retrospective analysis was carried out on the free beta human chorionic gonadotrophin (beta-hCG) and pregnancy associated plasma protein-A (PAPP-A) levels and nuchal translucency thickness in 49 653 women with a normal singleton fetus who had first trimester combined screening for Down Syndrome in three centres. Median MoMs and the distribution of log MoMs of the two markers were compared in two groups-7470 women who self-reported vaginal bleeding and 42 183 women who reported no vaginal bleeding at any stage prior to the screening test. RESULTS: The overall median MoM free beta-hCG and that in the bleeding and non-bleeding group were 0.9854, 1.0012 and 0.9832, and for PAPP-A were 1.0407, 1.0413 and 1.037. There was no significant difference between the bleeding and non-bleeding group by median test (p = 0.080) or by t-test comparing log MoMs (p = 0.1305) for free beta-hCG and for PAPP-A with median test (p = 0.5071) or by t-test comparing log MoMs (p = 0.1740). For delta nuchal translucency (NT) there was also no significant difference between the bleeding and non-bleeding group (p = 0.055). CONCLUSION: Vaginal bleeding has little or no impact on first trimester marker levels and no correction is necessary.
Abstract: BACKGROUND: Maternal serum A Disintergrin And Metaloprotease-12 (ADAM-12) has been proposed as a marker for prenatal screening of chromosomal abnormalities, pre-eclampsia and other adverse pregnancy outcomes. In this study, we examine the stability of ADAM-12 with time and at different temperatures. METHODS: Maternal serum and whole blood pools were stored at 30 degrees C, room temperature and refrigerator temperature or subjected to repeated freeze-thaw cycles. ADAM-12 was measured at set time points using an automated DELFIA research assay. RESULTS: Using a 10% change in concentration as a limit of stability, ADAM-12 is stable in serum for less than 15 h at 30 degrees C, less than 20 h at room temperature and for 51 h at refrigerator temperature. ADAM-12 levels are not altered following three - 20 degrees C to room temperature freeze-thaw cycles. The stability of ADAM-12 in whole blood appears similar to that in serum. CONCLUSIONS: The findings of this study suggest that ADAM-12 may be unstable under many routine laboratory conditions, and the marker's instability may also be partly responsible for the discrepancies in the literature.
Abstract: To investigate the predictive value of the combination of first-trimester serum placental protein 13 (PP13), uterine artery Doppler pulsatility index (PI) and pulse wave analysis (augmentation index at a heart rate of 75 beats per min (AIx-75)), and to evaluate concurrent and contingent strategies using this combination for assessing the risk of pre-eclampsia in high-risk women.
Abstract: OBJECTIVE: To asses whether supra elevated levels of maternal serum free beta hCG in the first trimester are associated with impaired renal function. METHOD: A cohort of 553 women with maternal serum free beta-hCG greater than 5 multiple of median (MoM) with a single euploid fetus was matched with a control of the same maternal age (+/-1 year), ethnic origin and with a free beta-hCG within the range 0.50-1.50 MoM. Screening samples were analysed for serum creatinine and estimated glomerular filtration rate was calculated. Renal function in the two groups was compared. The database was examined to find outcomes registered as known renal disease amongst the high free beta-hCG group. RESULTS: In the group with a supra elevated free beta-hCG MoM there was a significant reduction in estimated glomerular filtration rate (eGFR) (122.85, 95% CI 120.43-124.74 vs 118.80, 95% CI 114.90-121.59; p = 0.009) suggesting a small but increased risk of renal disease. CONCLUSIONS: The presence of renal disease should also be considered as one potential cause of supra elevated levels of free beta-hCG in addition to the possibility of paternally derived triploidy and trisomy 21.
Abstract: BACKGROUND: The aim was to evaluate the role of serum inhibin A and activin A in the prediction of the outcome of women with 'pregnancies of unknown location' (PULs). METHODS: Serum human chorionic gonadotrophin (hCG), progesterone, inhibin A and activin A levels were measured at 0 and 48 h. Differences in the mean levels and the change in levels over 48 h expressed as a ratio (48/0 h) were examined between the three outcome groups--failing PUL, intrauterine pregnancy (IUP) or ectopic pregnancy. Variables were incorporated into logistic regression models to predict the pregnancy outcomes, which were evaluated using receiver operator characteristic curves. RESULTS: One hundred and forty-one women were classified as PULs: 67 failing PULs (47.5%), 58 IUPs (41.1%) and 16 ectopic pregnancies (11.4%). Activin A levels were not significantly different between the three outcome groups. Inhibin A levels were significantly lower in failing PULs. The logistic regression model based on serum inhibin levels gave an area under the curve (AUC) of 0.88 for failing PUL, 0.87 for IUP and 0.60 for ectopic pregnancy. The model based on serum activin levels gave an AUC of 0.61 for failing PUL, 0.64 for IUP and 0.51 for ectopic pregnancy, and the model based on serum hCG levels gave an AUC of 0.95 for failing PUL, 0.97 for IUP and 0.67 for ectopic pregnancy. CONCLUSIONS: Serum activin A levels at 0 and 48 h are not helpful in predicting the outcome of PULs. Although serum inhibin A levels may be of use in the prediction of failing PULs and IUPs in the PUL populations, they do not perform as well as serum hCG levels.
Abstract: OBJECTIVE: To re-evaluate in a larger cohort of patients if the maternal serum biochemical markers used in first trimester aneuploidy screening have the same marker distributions in pregnancies with a previous history of aneuploidy compared with those that have no previous history. METHODS: Information related to previous pregnancy history is routinely recorded as part of first trimester screening in three centres King George, Kings College and Fetal Medicine Centre, London. From the database, records were extracted for women who had a previous pregnancy diagnosed with trisomies 13, 18 or 21. For each woman with a previous aneuploidy, five unaffected pregnancies in women of the same maternal age and with no previous aneuploidy pregnancy were selected as controls. A comparison was made between the marker distributions for pregnancy associated plasma protein-A (PAPP-A) and free beta-human chronic gonadotrophin (beta-hCG) amongst the cases and controls using nonparametric statistical tests. RESULTS: A series of 8240 controls were compared against group of 1032 cases with a previous trisomy 21, 293 with a previous trisomy 18 and 158 with a previous trisomy 13. Cases with multiple previous trisomies were excluded. There were no significant differences in the level of free beta-hCG; however, in cases of trisomy 21 and trisomy 13 the levels of PAPP-A were increased by 5 and 16%, respectively. CONCLUSION: Risk calculation algorithms may need to take account of the increased PAPP-A levels in women with a previous trisomy 21 or trisomy 13.
Abstract: OBJECTIVE: To investigate if fetal sex has an impact on 1st trimester combined screening for aenuploidy. METHODS: We studied the first trimester PAPP-A, free beta-human chorionic gonadatropin (beta-hCG) and nuchal translucency levels in 56,024 normal, singleton pregnancies with known fetal sex at birth. We also examined the distributions in 722 pregnancies with trisomy 21 of known fetal sex. RESULTS: We have found a 14.74% increase in first trimester maternal serum (MS) median free beta-hCG MoM, 6.25% increase of PAPP-A and a 9.41% decrease in delta NT, when the fetus was female. Analysis of data has shown that women carrying a female fetus were 1.084 times more likely to be in the 'at risk' group than those carrying a male fetus. In examining data from 722 pregnancies in which the fetus was affected by trisomy 21, we observed a similar 20.8% increase in free beta-hCG MoM, 5.7% increase in PAPP-A and a 12% decrease in delta NT when the fetus was female. Amongst the trisomy 21 cases, 88.8% of male trisomy 21 cases were detected compared with 91.2% in female cases, this difference was not statistically significant. Correcting for fetal sex redressed the balance in screen-positive rate between the sexes and had a minimal impact on detection rate. CONCLUSION: Correcting for fetal sex may be a worthwhile consideration. A cost-benefit analysis would be required to determine if it is feasible to introduce fetal gender assignment into the routine first trimester scan for the purpose of marker correction and whether this would have any significant impact.
Abstract: OBJECTIVE: To examine whether maternal Rhesus status has any effect on the levels of first-trimester markers free beta-human chorionic gonadotropin (beta-hCG), pregnancy-associated plasma protein-A (PAPP-A) and nuchal translucency (NT). METHODS: First-trimester free-beta-hCG and PAPP-A levels from pregnant women attending three hospitals in Kent were converted into MoMs and corrected for maternal weight, ethnicity, and smoking status. Maternal Rhesus status data were merged with screening data and free-beta-hCG and PAPP-A medians multiples of medians (MoMs) and NT from the Rhesus positive and Rhesus negative group were compared. RESULTS: Totally, 15 045 normal, singleton pregnancies were retrieved with full records. Altogether, 16.0% of the population were Rhesus negative. There was no difference between the medians MoMs of both free-beta-hCG nor PAPP-A nor NT in the two Rhesus status groups (p > 0.05). Demographic analysis on the distribution of Rhesus status in different ethnic origins showed that Caucasians have lower percentages of RhD-positive antigen compared to Asians and Afro-Caribbeans. CONCLUSION: Maternal Rhesus status does not influence the levels of free-beta-hCG and PAPP-A in the first trimester of pregnancy in this almost exclusively Caucasian population studied; therefore correction for maternal Rhesus status is not suggested.
Abstract: OBJECTIVE: To evaluate whether first trimester maternal serum PP13 can predict pre-eclampsia among women with a priori high risk. METHOD: This was a nested case-control study. Women less than 14 weeks' gestation at increased risk of developing pre-eclampsia were recruited. Venous blood samples were assayed for PP13 using enzyme-linked immunosorbent assay. PP13 multiples of median (MoM) were calculated and adjusted for body mass index, ethnicity, smoking, maternal age and parity. For each case of pre-eclampsia (n = 42), five controls were randomly selected. PP13 levels were compared between women who developed pre-eclampsia and controls using the Wilcoxon rank sum test. Sensitivity and false-positive rates were derived from receiver operating characteristic curves. RESULTS: Women who developed pre-eclampsia had significantly lower (P < 0.001) PP13 MoMs compared with controls. PP13 MoMs for controls and pre-eclampsia cases were 1.0 (range 0.0-10.0) and 0.4 (range 0.0-7.0), respectively (P < 0.001). At a MoM cutoff of 0.53, for a false-positive rate of 10%, sensitivity was 50% for pre-eclampsia at term (>37 weeks), 62% for preterm pre-eclampsia (<37 weeks) and 71% for early-onset pre-eclampsia (<34 weeks). CONCLUSION: First trimester PP13 can predict pre-eclampsia in women at increased a priori risk and predicts early-onset better than late-onset disease.
Abstract: BACKGROUND: ADAM12s (a disintegrin and metalloprotease) is a placenta-derived glycoprotein that is involved in growth and differentiation and has been shown to be a potential first-trimester and second-trimester marker of trisomy 21 and other aneuploides. Maternal ADAM12s concentrations show a considerable temporal variation with gestational age and in the initial study levels were found to be significantly reduced in the early first trimester. Here we study the levels prior to 10 weeks of gestation to establish further the effectiveness or otherwise of ADAM12s as an early screening marker. MATERIALS AND METHODS: Samples collected as part of routine first-trimester screening were retrieved from storage. In total, ten samples from singleton pregnancies with trisomy 21 were identified and were collected between the 8th and 9th weeks of gestation-of these 80% had been identified by combined first-trimester screening. A series of 62 gestational age-matched samples from singleton pregnancies collected during the same period formed the control group. ADAM12s was measured by a new DELFIA assay incorporating two monoclonals (6E6 and 8F8). Results were expressed as multiples of the median (MoM). RESULTS: The median MoM ADAM12s at a median gestation of 9.3 weeks was 0.61 which was significantly lower than in the controls (p = 0.011) when compared by the Mann-Whitney test. The corresponding median pregnancy associated plasma protein (PAPP-A) was 0.30 and free beta-human chorionic gonadotropin (beta-hCG) 2.02. CONCLUSIONS: Combining the data from this study and from the only other published study with data prior to 10 weeks suggests that ADAM12s may have the potential as an early screening marker for trisomy 21, but may not be as reduced as first thought.
Abstract: BACKGROUND: In a previous study, reduced levels of maternal serum placental protein 13 (PP13) in the first trimester have been correlated with adverse pregnancy outcomes. The objective of this study was to compare first-trimester PP13 levels in control pregnancies with pregnancies resulting in one or more of the following adverse outcomes: intrauterine growth restriction (IUGR), small and very small (3rd, 5th, 10th centile) for gestational age (SGA), low (<1.5 and < 2.5 kg) birth weight (LBW), macrosomia (the > 90th centile), large birth weight (>4.5 kg), preterm (35-36 weeks) and very early (<34 weeks) delivery (PTD), and intrauterine fetal demise (IUFD). METHODS: Maternal serum samples from 1940, 11 to 14 weeks singleton pregnancies, were assayed for PP13 and the concentrations were corrected for gestational age, maternal weight, smoking status, and ethnic origin. A comparison of the levels of PP13 in 364 controls and 1576 adverse outcome categories was made. PP13 levels were expressed in terms of both concentration and multiple of medians (MoMs). RESULTS: Comparison of PP13 MoMs from SGA, PTD, and low birth weight samples with control pregnancy samples showed no statistically significant difference. In macrosomic pregnancies (>90th centile), levels of PP13 were significantly higher than controls (p = 0.0263) although the number of cases in this study was small. CONCLUSION: Decreased levels of PP13 were not significantly correlated with the studied adverse pregnancy outcomes of IUGR, PTD low birth weight, and IUFD. Further studies are required to evaluate if measurement of PP13 has any value in the early assessment of pregnancies.
Abstract: OBJECTIVE: To examine the distribution of first-trimester biochemical markers of aneuploidy in twin pregnancies, and to assess whether there are differences in the distributions between monochorionic and dichorionic twins. METHODS: Maternal serum-free beta-hCG and PAPP-A were measured between 11 + 0 and 13 + 6 weeks as part of a routine first-trimester screening program in conjunction with fetal nuchal translucency (NT) performed at two sites. Data from twin pregnancies were extracted from the fetal databases along with information on the chorionicty. The individual marker concentrations were expressed as weight corrected, ethnicity corrected, smoking corrected and IVF corrected MoM using data from singleton pregnancies as the reference. The overall medians were compared to those in singleton pregnancies and between monochorionic and dichorionic twins. RESULTS: Data was available from 1914 sets of twins. Of these, 1214 had information with respect to chorionicity, with 1024 being dichorionic and 190 being monochorionic. The overall median weight corrected, ethnicity corrected, smoking corrected and IVF corrected MoM amongst twin pregnancies were 2.023 for free beta-hCG (sd log(10) MoM = 0.2611 and 2.121 for PAPP-A (sd log(10) MoM = 0.2255) -- both medians were significantly greater than the medians in singleton pregnancies (1.00 MoM). In the case of monochorionic and dichorionic twins the median weight corrected, ethnicity corrected, smoking corrected and IVF corrected, free beta-hCG MoM's were not significantly different (1.983 v 2.041), however for PAPP-A the median weight corrected, ethnicity corrected, smoking corrected and IVF corrected MoM in monochorionic twins was significantly lower than in dichorionic twins (1.756 v 2.250) whilst the sd log(10) MoM's were not significantly different (0.2185 v 0.2167). CONCLUSION: Screening in twin pregnancies requires adjustment of the calculated MoM to account for the presence of two fetuses. In general, for free beta-hCG, this should be by dividing the observed corrected MoM by 2.023. For PAPP-A two different factors are required - 2.192 in dichorionic twins and 1.788 in monochorionic twins.
Abstract: OBJECTIVES: To examine the clinical utility of the first-trimester biochemical markers of aneuploidy in their ability to predict subsequent delivery of a small-for-gestational age (SGA) infant. METHODS: We examined singleton pregnancies with no chromosomal abnormality and with complete outcome data that had undergone screening for trisomy 21 by a combination of fetal nuchal translucency (NT) thickness and maternal serum free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11 + 0 and 13 + 6 weeks' gestation. The biochemical markers were converted to multiples of the expected normal median (MoM) for a pregnancy of the same gestation. The association between free beta-hCG and PAPP-A and the incidence of SGA were assessed by comparing the relative incidence at MoM cut-offs and birth-weight centile cut-offs. At various marker levels the likelihood ratios (LR) for SGA were also calculated after excluding other adverse pregnancy complications. RESULTS: There were 46,262 pregnancies resulting in live births with birth weight at or above the 10(th) centile, and 3,539 below the 10(th) centile for gestation (SGA). There was a significant inverse association between the risk for SGA and maternal serum PAPP-A MoM but not free beta-hCG MoM. At the 5(th) centile of the normal outcome group for PAPP-A (0.415 MoM) the odds ratios for SGA below the 10(th), 5(th) and 3(rd) centiles of normal were 2.70, 3.21 and 3.66 and the respective detection rates for SGA were 12.0%, 14.0% and 16.0%. CONCLUSIONS: Low levels of maternal serum PAPP-A are associated, in the absence of an abnormal karyotype, with an increased risk for subsequent delivery of an SGA infant.
Abstract: BACKGROUND: Low levels of pregnancy associated plasma protein-A (PAPP-A) have been previously shown to be associated with pregnancies that subsequently develop pre-eclampsia. The objective of this study was to establish the relative risk for pre-eclampsia at various PAPP-A levels as an aid to counselling and follow up of pregnancies. METHODS: Maternal serum PAPP-A and free ss-human chorionic gonadotropin (ss-hCG) levels at 11 to 13 weeks of gestation from 224 singleton pregnancies that subsequently developed pre-eclampsia were compared to those from 47,770 normal singleton pregnancies resulting in live births after 37 weeks with birth weight greater than or equal to the 10th centile of normal for gestation. In all cases, the measured PAPP-A and free ss-hCG levels were expressed as multiple of the median (MoM). The association between metabolite levels and the incidence of pre-eclampsia was assessed by comparing the relative incidence at a number of MoM cut-offs and at various centiles. At various marker levels, the likelihood ratio for pre-eclampsia was also calculated. RESULTS: In the pre-eclampsia group the median PAPP-A MoM was significantly reduced (0.772 MoM, p < 0.0001) whilst the median free beta-hCG MoM was not different from controls (0.981 MoM, p = 0.26). With decreasing levels of PAPP-A, the likelihood ratio for pre-eclampsia increased. At the 5th centile of normal (PAPP-A MoM 0.415) the odds ratio was increased 4-fold and at this cut-off 15% of cases of pre-eclampsia would be identified. CONCLUSIONS: The graphical presentation of a likelihood ratio curve for pre-eclampsia at any PAPP-A MoM level is likely to be useful in counselling women with low levels of PAPP-A and a normal karyotype. Use of low levels of PAPP-A for selecting women for further follow-up with uterine artery Doppler may further improve the clinical discrimination.
Abstract: OBJECTIVE: To examine the distribution of placental growth factor (PlGF), vascular endothelial growth factor (VEGF) and soluble VEGF receptor-1 (sFlt-1) in maternal and embryonic fluid compartments in early pregnancy. METHOD: The concentrations of PlGF, VEGF and sFlt-1 were measured in coelomic fluid and maternal serum from 16 singleton pregnancies at 7.0-9.3 weeks. In six cases, amniotic fluid was also examined. RESULTS: The median concentration of PlGF was 14.1 (range 8.9-27.6) pg/mL in maternal serum, 13.9 (range 9.5-31.4) pg/mL in coelomic fluid and 8.9 (range 3.9-15.3) pg/mL in amniotic fluid. The concentration of PlGF increased between 7.0 and 9.3 weeks in maternal serum (p = 0.001) and decreased in coelomic and amniotic fluid (p = 0.001). The median concentration of sFlt-1 was 8561 (range 6724-10 673) pg/mL in coelomic fluid, 523 (range 244-986) pg/mL in maternal serum, 30 (range 12-83) pg/mL in amniotic fluid (p = 0.0001), and it did not change significantly with gestation. VEGF was undetectable in most of the samples, and therefore, no further analysis was performed. CONCLUSION: PlGF and sFlt-1 are present in the maternal and fetal fluid compartments in very early pregnancy, and their distribution is consistent with their site of production and the local conditions of transport.
Abstract: BACKGROUND: Here we study the levels of ADAM12s prior to and after 10 weeks of gestation to establish further the effectiveness or otherwise of ADAM12s as an early screening marker. MATERIALS AND METHODS: Samples collected as part of routine first-trimester screening were retrieved from storage at - 80 degrees C. In total, 55 samples from pregnancies with trisomy 21 were identified, 31 collected between the 6th and 9th weeks of gestation and 24 collected after the 10th week. A series of 567 gestational age-matched samples collected during the same period formed the control group. RESULTS: The median, multiples of the median (MoM) ADAM12s, at a median gestation of 10.0 weeks was 0.66, which was significantly lower than in the controls (p = < 0.001) when compared by Mann-Whitney test. The median MoM in those cases (n = 31) collected prior to 10 weeks was 0.618 MoM at a median gestation of 9.1 weeks. In those collected prior to 9 weeks (n = 14) the median was 0.596 at a median gestation of 8.6 weeks. CONCLUSIONS: The data from this study does not support data from a previous study showing ultra-low levels of ADAM12s in pregnancies affected by trisomy 21 prior to 10 weeks of gestation.
Abstract: OBJECTIVE: To evaluate whether measurement of maternal serum inhibin-A and activin-A at 11 + 0 to 13 + 6 weeks of gestation, alone or in combination with second-trimester uterine artery pulsatility measured by Doppler velocimetry, is useful in predicting those women who will develop pre-eclampsia. METHODS: This was a nested case-control study of pre-eclampsia cases with controls matched for gestational age and storage time for the maternal serum. Samples were collected as part of a first-trimester prenatal chromosomal anomaly screening program. Activin-A and inhibin-A were measured using a commercial enzyme-linked immunosorbent assay and the clinical outcomes were blinded to the operator. All the patients underwent uterine artery Doppler flow velocimetry to measure the mean pulsatility index at 22-24 weeks' gestation. RESULTS: In total there were 64 cases with pre-eclampsia, with 34 delivering prior to 35 weeks of gestation. The control group included 240 cases. In the control group the levels of activin-A and inhibin-A did not change across the narrow gestational window and the median levels were 2.16 ng/mL and 231.13 pg/mL, respectively. In the pre-eclamptic group levels of activin-A and inhibin-A were significantly increased, at 2.52 ng/mL and 286.64 pg/mL (1.24 multiples of the median (MoM) and 1.17 MoM, respectively). There was no difference in the median MoM in those delivering prior to 35 weeks and those delivering later. At cut-offs of the 90(th) centile of normal, activin-A and inhibin-A levels would have identified 20% and 35%, respectively, of cases that would develop pre-eclampsia. When combined with uterine artery Doppler, activin-A measurement could have increased the detection rate from 55% to 63% and inhibin-A measurement could have increased it to 68% at a 5% false positive rate. CONCLUSION: Although increased in the first trimester, levels of activin-A and inhibin-A are probably too low to make a significant contribution to screening for pre-eclampsia at this time.
Abstract: BACKGROUND: ADAM12s is a placenta-derived glycoprotein that is involved in growth and differentiation, and has been shown to be a potential first-trimester and second-trimester marker of Trisomy 21 and other aneuploides. Maternal ADAM12s concentrations show a considerable temporal variation with gestational age and here we study the levels at 11-13 weeks of gestation to establish the effectiveness or otherwise at a time when other established markers are used. MATERIALS AND METHODS: Samples collected as part of routine first-trimester screening were retrieved from storage. In total, 46 samples from pregnancies with Trisomy 21 were identified and collected between 11 and 13 weeks of gestation-of these 83% had been identified by combined first-trimester screening. A series of 414 gestational age-matched samples collected during the same period formed the control group. ADAM12s was measured by a new DELFIA assay incorporating two monoclonals (6E6 and 8F8). Results were expressed as weight-corrected multiples of the median (MoM). RESULTS: The median MoM ADAM12s rose from 0.914 at 11 weeks to 1.032 at 13 weeks. CONCLUSIONS: Combining the data from this study and other published studies suggests that ADAM12s is unlikely to be of much additional value when screening for Trisomy 21 in the period 11-13 weeks. More studies are required looking at the potential of ADAM12s prior to 10 weeks.
Abstract: OBJECTIVE: To examine whether maternal serum ADAM12s, a potential first- and second-trimester marker of fetal aneuploidy and fetal growth, had altered concentrations in the first or second trimester of pregnancies subsequently developing pre-eclampsia. METHODS: ADAM12s was measured by a time-resolved fluoroimmunoassay developed by PerkinElmer Life Science. Maternal serum samples from women taking part in early first-trimester aneuploidy screening in whom the pregnancy resulted in pre-eclampsia (64) were identified from a cohort of 4,390 singleton pregnancies in which uterine artery Doppler mean Pulsatility Index (PI) had been measured at 22-24 weeks. From amongst those cases delivering a normal term infant with birth weight greater than the 10th centile for gestational age 240 cases were selected as gestational age-matched controls. A second study group consisting of maternal serum taken at 22-24 weeks at the time of uterine artery Doppler in a group of 12 women developing pre-eclampsia were compared with 86 matched controls from a previously studied cohort of 24 cases and 144 controls. Serum ADAM12s concentrations were converted to multiple of the median (MoM) to take account of gestational age variation. RESULTS: First-trimester maternal serum ADAM12s levels in women who developed pre-eclampsia were reduced with a median MoM of 0.71 which was further reduced in those delivering prior to 35 weeks (0.50). At the 5th centile of normal (0.48 MoM) ADAM12s identified 27% of cases with pre-eclampsia and 47% of those with early pre-eclampsia. Combining ADAM12s with PAPP-A from a previous study only resulted in a further 1% increase in detection of all women developing pre-eclampsia. However combining ADAM12s with mean PI increased the detection rate to 66%. In the second trimester at 22-24 weeks the maternal serum ADAM12s levels were increased in those women developing pre-eclampsia compared to controls (709 vs 486 ug/L, p = 0.045). CONCLUSION: ADAM12s in addition to being a potential marker of aneuploidy may also be a marker of pre-eclampsia. Further studies are required to see if this can improve on the clinical discrimination already provided by PAPP-A in the early first trimester.
Abstract: BACKGROUND: An initial study of trisomy 21 cases showed that prior to 10 weeks, maternal serum levels of intact hCG in the early first trimester are lower than normal. Here we further study the levels prior to and after 10 weeks of gestation to further establish whether or not the intact hCG is effective as a very early screening marker. METHODS: Fifty-nine samples from pregnancies with trisomy 21 were identified, 31 were collected between the sixth and ninth weeks of gestation and 28 after the tenth week. A series of 629 gestational age-matched samples collected during the same period formed the control group. Intact hCG was measured by a DELFIA assay. RESULTS: The multiples of the median (MoM) in cases (n = 31) collected prior to 10 weeks were 0.79 (CI 0.62-0.98) at a median gestation of 9.1 weeks. Prior to 9 weeks (n = 14) the median was 0.774 (CI 0.54-1.09) at a median gestation of 8.5 weeks. Modelling the detection rate for a 3 or 5% false-positive rate when screening using intact hCG, free beta-hCG and PAPP-A at 8-10 weeks of gestation indicated that 71 or 77% of cases would be detected. CONCLUSION: More data are needed to establish a secure MoM for intact hCG in pregnancies prior to 10 weeks, before it could be considered a suitable screening marker.
Abstract: OBJECTIVES: To use multiple regression analysis to define the contribution of maternal variables that influence the measured concentration of free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A), and the interaction between these covariates, in first-trimester biochemical screening for trisomy 21. METHODS: This was a multicenter study of prospective screening for trisomy 21 by a combination of fetal nuchal translucency thickness, and maternal serum free beta-hCG and PAPP-A at 11 + 0 to 13 + 6 weeks of gestation. In the pregnancies subsequently found to have trisomy 21 and in those with no obvious chromosomal abnormality, we used multiple regression analysis to account for pregnancy characteristics that influence the measured concentrations of free beta-hCG and PAPP-A. We fitted Gaussian distributions to the distribution of log multiples of the median (MoM) values in trisomy 21 and in unaffected pregnancies. RESULTS: There were 491 cases of trisomy 21 and 96 803 chromosomally normal pregnancies. Compared with values in Caucasian women, those who were parous, non-smokers and those who conceived spontaneously, PAPP-A was 57% higher in women of Afro-Caribbean origin, 3% higher in South Asians, 9% higher in East Asians, 2% higher in nulliparous women, 17% lower in smokers and 10% lower in those conceiving by in-vitro fertilization (IVF). Free beta-hCG was 12% higher in women of Afro-Caribbean origin, 9% lower in South Asians, 8% higher in East Asians, 2% higher in nulliparous women, 4% lower in smokers and 9% higher in those conceiving by IVF. In screening for trisomy 21 by maternal age and serum free beta-hCG and PAPP-A the estimated detection rate was 65% for a false-positive rate of 5%. CONCLUSIONS: In first-trimester biochemical screening for trisomy 21 it is essential to adjust the measured values of free beta-hCG and PAPP-A for maternal and pregnancy characteristics.
Abstract: OBJECTIVE: To assess whether the maternal serum ADAM12s concentrations are altered in the first and second trimester of pregnancies complicated by rare aneuploides. METHODS: ADAM12s was measured by a semi-automated time-resolved immunofluorometric assay in a series of 60 first-trimester cases with trisomy 13, 78 first-trimester cases with Turner's syndrome, 38 first-trimester cases with triploidy and 24 first-trimester cases with sex aneuploidy-the cases were compared with the data from 389 first-trimester controls. In the second trimester, a smaller number of 6, 7, 2 and 13 cases, respectively, were compared with the data from 341 controls. All data were expressed as multiple of the median (MoM) and corrected for maternal weight. Correlation with previously analysed markers (PAPP-A, free beta-hCG and delta NT) was performed. RESULTS: The first-trimester median MoM ADAM12s was significantly lower than 1.0 in all types of rare aneuploidy with the possible exception of triploidy type II. A significant positive correlation with gestational age was reported for trisomy 13 and Turner's syndrome. ADAM12s was not significantly correlated with any other first-trimester marker. In the second trimester, ADAM12s values were marginally increased in these rare aneuploidies. CONCLUSIONS: ADAM12s has already been shown to be a possible early first- and second-trimester marker of trisomies 21 and 18. Our data also show the possibility of levels of this marker being altered in the first and second trimester of pregnancies with rare aneuploidies. This may be a useful addition to screening strategies in the future.
Abstract: OBJECTIVE: To investigate the potential utility of first trimester screening for Down syndrome using Free beta-hCG, total hCG and PAPP-A. MATERIALS AND METHODS: Using estimates from the literature, a simulation study was undertaken to estimate the performance of tests incorporating, Free beta-hCG, total hCG and PAPP-A at gestations of 8-12 weeks. We used sensitivity analysis to assess the effect of departures from the assumed model. RESULTS: We estimate that detection rates in excess of 75% for a false positive rate (FPR) of 3% can be achieved with first trimester measures of PAPP-A, total hCG and Free beta-hCG at 8 weeks-the addition of total hCG adding 11%. Detection rates of around 90% for a FPR of 3% can be achieved through the inclusion of nuchal translucency (NT) at 12 weeks to these early first trimester biochemical markers. Our analysis indicates that the marginal benefit of adding total hCG diminishes rapidly with gestational age and that there is little benefit from adding total hCG later than 10 weeks of gestation. CONCLUSION: The performance of first trimester screening using early combinations of total hCG, Free beta-hCG and PAPP-A should be assessed in further studies.
Abstract: This article reviews the performance of first trimester screening for chromosomal anomalies using various combinations of ultrasound and maternal serum biochemical modalities. Detection rates in excess of 90% can be routinely achieved for Trisomy 21, Trisomy 13, Trisomy 18 using a combination of fetal nuchal translucency (NT) thickness and maternal serum free ss-hCG and PAPP-A at 11 + 0 to 13 + 6 weeks of gestation.
Abstract: OBJECTIVE: To examine the effectiveness of first-trimester fetal trisomy 21 screening using a combination of maternal age, nuchal translucency thickness (NT) and maternal serum free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) levels in a predominantly Chinese population in Hong Kong. METHODS: This was a prospective study over a 1.5-year period of 2990 women who underwent combined screening for trisomy 21 between 11+0 and 13+6 weeks of gestation in a university fetal medicine unit. NT was measured according to the criteria set by The Fetal Medicine Foundation (FMF), maternal serum free beta-hCG and PAPP-A levels were measured, and the risk of trisomy 21 was calculated using The FMF's algorithm. Fetal karyotyping was advised when the risk was 1 : 300 or above. All subjects were followed up for pregnancy and fetal outcome. RESULTS: Of the 2990 women who underwent the screening program, 99% were Chinese. There were 57 twin pregnancies, giving a total of 3047 fetuses. Thirty-one percent of the women were 35 years old or above. One hundred and eighty-five (6.1%) fetuses were screen-positive; this included 14 cases of trisomy 21 and 17 cases of other chromosomal abnormalities. The positive predictive value was 16.7%. Among the 2862 screen-negative fetuses, only 18 (0.6%) cases had an unknown fetal outcome. There were no cases in which trisomy 21 was missed and the infant was liveborn. CONCLUSION: First-trimester combined screening for fetal trisomy 21 is highly effective among Chinese subjects.
Abstract: OBJECTIVES: To evaluate whether first-trimester levels of PAPP-A and serum free-beta-human chorionic gonadotrophin (free beta-hCG) vary with maternal blood group and rhesus status and to assess whether this has implications for first-trimester screening for chromosomal anomalies. METHODS: Blood group and rhesus status information was extracted from birth records for women undergoing first-trimester screening. The birth records were combined with prenatal screening records by an in-house developed record linkage software. In 2252 singleton pregnancies of normal obstetric outcome, the median weight-corrected, ethnicity-corrected and smoking-corrected MoM were compared in the various blood groups, using t-tests after log10 transformation of the marker MoM against the whole study group. RESULTS: Only those women with a B rhesus positive blood group had statistically significant higher MoM levels of PAPP-A (0.995 v 0.937). CONCLUSIONS: A larger study is required to establish the validity of this increase in PAPP-A in the B rhesus positive group. If this can be substantiated, the elevation in PAPP-A in this group may require correction when screening for chromosomal anomalies.
Abstract: BACKGROUND: ADAM12 (a disintegrin and metalloprotease 12) is a placentally derived glycoprotein that appears to be involved in growth and differentiation. The maternal serum concentration of ADAM12 appears to be a very good marker of trisomy 21 in the early first trimester when levels are reduced, and in the second trimester around 16-18 weeks levels are elevated. One small preliminary study of first trimester pregnancies with trisomy 18 found reduced levels in the maternal serum, and we examine herein the potential of ADAM12 as a marker of trisomy 18 in both the first and second trimester of pregnancy. MATERIALS AND METHODS: The concentration of ADAM12 was determined by a time-resolved immunofluorometric assay in 132 first and 12 second trimester cases of trisomy 18, and 389 first and 341 second trimester gestational age-matched control pregnancies. Medians of normal pregnancies were established by polynomial regression and used to determine the population distribution parameters for the trisomy 18 and control groups. Correlation with previously established pregnancy-associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin (beta-hCG) multiples of the median (MoMs) and nuchal translucency thickness (NT) MoM were determined and used to model the performance of first trimester screening with ADAM12 in combination with other first trimester markers. RESULTS: The maternal serum concentration of ADAM12 in the first trimester was significantly reduced with a median MoM of 0.829 (p < 0.001) and a mean log10 MoM SD of 0.2663 compared to 0.3353 in the controls. In the second trimester small series ADAM12 was significantly increased with a median MoM of 2.09 (p = 0.001) and a mean log10 MoM SD of 0.2607 compared to 0.4318 in controls. There was a significant correlation of ADAM12 MoM with gestational age (r = 0.510) in trisomy 18 cases, and the median MoM increased from 0.51 at 10 weeks to 1.28 at 13 weeks and 2.09 across the 14-18 week window. ADAM12 was correlated with PAPP-A (r = 0.1918) in the first trimester of cases with trisomy 18 but less so with NT (r = 0.1594) and free beta-hCG (r = 0.0938). Modeled detection rates incorporating ADAM12, free beta-hCG, and NT were 92% at 1% false positive rate (88% at 0.5%) A combination of all four markers had a detection rate of 96.5% at a false positive rate of 1% (95% at 0.5%). CONCLUSION: ADAM12 may be a useful addition to early screening for trisomy 18 alongside other chromosomal anomalies, particularly if biochemical screening can occur before 10 weeks.
Abstract: OBJECTIVE: To evaluate whether measurement of maternal serum PP13 at 22 to 24 weeks of gestation, alone or in combination with second-trimester biochemical markers or uterine artery pulsatility measured by Doppler velocimetry, is useful in predicting those women at risk of developing pre-eclampsia. STUDY DESIGN: A nested case-control study of pre-eclampsia cases with controls matched for gestational age and storage time for the maternal serum. PP13 was tested by an ELISA, with the samples blinded to pregnancy outcome. All patients also underwent uterine artery Doppler flow velocimetry at 22-24 weeks to measure the mean pulsatility index (PI). Results for Inhibin, Activin, PAPP-A and Free beta-hCG were available from previous studies. RESULTS: There were 73 controls and five cases with early pre-eclampsia in which delivery was induced prior to 35 weeks. In addition, there were a further seven cases with pre-eclampsia in which delivery was not induced before term. Median PP13 levels for controls and all cases were 295.9 and 212.6 pg/ml, and 171.2 pg/ml amongst the early pre-eclampsia cases, with the MoMs 1.00, 0.94 and 0.63, respectively (p < 0.001). Receiver operator characteristic (ROC) curve analysis for either all cases or early cases versus controls yielded areas under the curve of 0.588 (95% CI: 0.42-0.76; p = 0.1526) and 0.693 (0.47-0.92; p = 0.0441) for PP13. At a specificity set to 0.80, the sensitivity for PP13 in the early cases was 0.40 and that in all cases was 0.25. Combining PP13 bivariately with any of the markers (PI, PAPP-A, Activin, Inhibin or Free beta-hCG) tested in the 22-24 week period did not improve the detection of early, late or all cases of pre-eclampsia compared with either marker alone. CONCLUSION: Late second-trimester PP13 alone is unlikely to be useful in predicting pre-eclampsia and early pre-eclampsia, and its prediction does not increase when coupled with second-trimester Doppler PI or other potential biochemical markers. Measuring between-trimester temporal changes may be worthy of further investigation.
Abstract: OBJECTIVE: To evaluate whether measurement of maternal serum placental protein-13 (PP-13) and pregnancy-associated plasma protein-A (PAPP-A) at 11 + 0 to 13 + 6 weeks of gestation alone or in combination with second-trimester uterine artery pulsitility measured by Doppler velocimetry is useful in predicting those women who will develop pre-eclampsia METHODS: This was a nested case-control study of pre-eclampsia cases with controls matched for gestational age and storage time for the maternal serum. Samples were collected as part of a first-trimester prenatal chromosomal anomaly screening program and were routinely tested for PAPP-A. PP-13 was tested using an enzyme linked immunosorbent assay (ELISA) by an examiner who was blinded to pregnancy outcome. All patients also underwent uterine artery Doppler flow velocimetry to measure the mean pulsatility index (PI) at 22-24 weeks' gestation. RESULTS: There were 446 controls and 44 cases with early pre-eclampsia where delivery was induced prior to 35 weeks. In addition there were a further 44 cases with pre-eclampsia in which delivery was not induced before term. Median PP-13 levels for controls, all cases and early pre-eclampsia cases were 176.9, 121.9 and 111.7 pg/mL, with multiples of the median (MoMs) of 1.00, 0.69 and 0.63, respectively (P < 0.001). PAPP-A MoMs were 1.00, 0.89 (P = 0.076) and 0.89 (P = 0.042) and mean PIs were 1.0, 1.6 (P < 0.001) and 1.7 (P < 0.001) for controls, all cases and early cases, respectively. Receiver-operating characteristics (ROC) curve analysis for either all cases or early cases vs. controls yielded areas under the curve for PP-13, PAPP-A and PI respectively of 0.68 (95% CI, 0.61-0.74; P < 0.001), 0.56 (95% CI, 0.49-0.63; P = 0.076) and 0.79 (95% CI, 0.72-0.87; P < 0.001) for all cases and 0.71 (95% CI, 0.63-0.79; P < 0.001), 0.59 (95% CI, 0.51-0.68; P = 0.076) and 0.86 (95% CI, 0.77-0.94; P < 0.001) for early cases. At a specificity set to 0.80 the sensitivities were 0.50, 0.23 and 0.76 for PP-13, PAPP-A and PI in the early cases and 0.44, 0.24 and 0.73 in all cases. Combining PP-13 and PI using logistic regression analysis yielded an area under the curve of 0.84 (95% CI, 0.78-0.90; P < 0.001) and a sensitivity of 0.74 in all cases, and 0.90 (95% CI, 0.84-0.96; P < 0.001) and a sensitivity of 0.79 for early cases. PAPP-A with PI gave an area under the curve of 0.82 (95% CI, 0.76-0.90; P < 0.001) and a sensitivity of 0.76 in all cases. Combining PAPP-A with PP-13 and PI did not add significantly to the sensitivity. CONCLUSION: First-trimester PP-13 levels may be useful in predicting pre-eclampsia and early pre-eclampsia, and the accuracy of the method increases when coupled with second-trimester Doppler PI measurement. First-trimester PAPP-A provides some prediction for pre-eclamspia when combined with PI but does not add to the prediction of early pre-eclampsia when PP-13 and PI are used together. Further studies are required to establish the real value of PP-13 in first-trimester screening for pre-eclampsia.
Abstract: BACKGROUND: PAPP-A is a marker used as part of the most effective method of screening for chromosomal anomalies in the first trimester. ADAM12 is a recently discovered pregnancy associated member of the ADAM (a multidomain glycoprotein metalloprotease) family. Recently, ADAM12 has been shown as a potential marker for early screening for chromosomal anomalies. Both PAPP-A and ADAM12 have been identified as proteases to insulin-like growth factor binding proteins. In this role, they may have a regulatory function in controlling the amount of free bioactive insulin-like growth factor (IGF). We therefore wish to examine if the levels of either of these proteases are related to various growth related adverse pregnancy outcomes. MATERIALS AND METHODS: PAPP-A and ADAM12 were measured in a subset of samples collected at 11 to 14 weeks as part of an OSCAR clinic screening for chromosomal anomalies. Follow-up of pregnancies screened between September 1999 and August 2003 identified 1705 pregnancies with an outcome of intrauterine fetal demise on or after 24 weeks, preterm delivery at 24-34 weeks or 35-36 weeks, very low birthweight (<1.5 kg), low birthweight (<2.5 kg), large birthweight (>4.5 kg), and birth weight below the 3rd or 5th or 10th centile for gestation. A series of 414 normal outcome pregnancies constituted the control group.Marker levels were adjusted for gestation and maternal weight and the log MoM of the markers were compared using t-test of unequal variance between the control group and the various adverse outcome groups. RESULTS: ADAM12 and PAPP-A concentrations were reduced in low for gestational age birth weights and in all births with weights below 2.5 kg. There was a linear relationship between the severity of the IUGR and the decrease in PAPP-A and ADAM12. In the larger babies, only ADAM12 was found to be significantly increased in babies above the 90th centile of weight for gestation. CONCLUSIONS: The results of our study are compatible with the proposed role of ADAM12 and PAPP-A in promoting growth and development by breaking down IGF binding proteins and causing the release of free IGF for uptake into cells to promote growth. In those cases that eventually result in poor fetal growth, levels of PAPP-A and ADAM12 at 11-14 weeks are significantly lower than normal-in this instance, lowered PAPP-A and ADAM12 would result in less free IGF being available for cell uptake and growth stimulation. Further studies may elucidate if screening using such modalities can lead to new potential treatments for poorly growing fetuses.
Abstract: BACKGROUND: ADAM 12 is a placenta-derived glycoprotein that is involved in growth and differentiation. The maternal serum concentration of ADAM 12 is a potential first-trimester maternal serum marker of Down syndrome (DS). Here we examine the potential of ADAM 12 as a second-trimester maternal serum marker of DS. MATERIALS AND METHODS: The concentration of ADAM 12 was determined in gestational week 14-19 in 88 DS pregnancies and 341 matched control pregnancies. Medians of normal pregnancies were established by polynomial regression and the distribution of log(10) MoM ADAM 12 values in DS pregnancies and controls determined. Correlations with alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (free beta-hCG) were established and used to model the performance of maternal serum screening with ADAM 12 in combination with other second-trimester serum markers. RESULTS: The ADAM 12 maternal serum concentration was significantly increased with a median MoM of 1.85 and a mean log(10) MoM (SD) of 0.268 (0.2678) compared to a mean log(10) MoM (SD) of 0.013 (0.4318) in controls. ADAM 12 correlated with maternal weight and ethnicity (with the serum concentration increased in Afro-Caribbeans), but neither with maternal age nor gestational age, and only marginally with AFP (r(DS) = 0.078, r(controls) = 0.093) and free beta-hCG (r(DS) = 0.073, r(controls) = 0.144. The increase in detection rate-for a false positive rate of 5%--by adding ADAM 12 to the double test (AFP + free beta-hCG) was 4%, similar to that of adding uE3 to the double test. CONCLUSION: ADAM 12 is an efficient second-trimester marker for DS. Further studies should be conducted to determine whether it may be a useful additional or alternative marker to those currently used in the second-trimester.
Abstract: OBJECTIVE: To examine whether in smokers there is a significant dose dependency between the number of cigarettes per day and levels of free ss-hCG and pregnancy-associated plasma protein A (PAPP-A) at 11-13(+6) weeks of gestation. METHODS: This was a retrospective analysis of the maternal serum free ss-hCG and PAPP-A levels in relation to the maternal smoking status in 109 263 chromosomally normal singleton pregnancies that had undergone first-trimester screening for Down syndrome by a combination of fetal nuchal translucency thickness and maternal serum biochemistry. RESULTS: There were 95 287 nonsmokers and 13 976 cigarette smokers. The overall median PAPP-A MoM among cigarette smokers was 0.827, which was 19.6% lower than the value of 1.029 in nonsmokers (p < 0.0001 for log(10) MoM). The respective values for beta-hCG MoM were 1.003 for smokers and 1.035 for nonsmokers (p < 0.0001 for log(10) MoM) which corresponds to a reduction of 3.1%. There was a significant inverse relationship between the number of cigarettes per day and the level of PAPP-A MoM (r = 0.989, p < 0.0001) but not the level of free beta-hCG MoM (r = 0.733; p = 0.098). Using a statistical modeling approach we found that the screen-positive rate when correcting the PAPP-A MoM by an all or nil smoking factor was reduced by only 0.1% (3.75 vs 3.85%) when compared to correcting with a factor related to the smoking dose per day. CONCLUSION: In first-trimester screening for Down syndrome by maternal serum PAPP-A and free beta-hCG the impact of correcting for the dose dependant rather than the all or nil effect of smoking is marginal. However, a dose dependent correction improves the accuracy of the individual patient-specific risk.
Abstract: OBJECTIVE: The purpose of this study was to examine the sonographic features of trisomy 13 at 11 to 13(+6) weeks of gestation. STUDY DESIGN: This was a retrospective study that examined the features of trisomy 13 at the ultrasound scan at 11 to 13(+6) weeks of gestation, which in our center is performed for the measurement of crown-rump length, nuchal translucency thickness, and fetal heart rate and the examination for major defects. RESULTS: In the 181 fetuses with trisomy 13, there were holoprosencephaly, exomphalos, and/or megacystis in 92 fetuses (50.2%), fetal heart rate above the 95th percentile in 129 fetuses (71.3%), and nuchal translucency above the 95th percentile in 141 fetuses (77.9%). There was no significant association between nuchal translucency and fetal heart rate, and it was estimated that inclusion of fetal heart rate in nuchal translucency screening can improve the detection rate of trisomy 13 by approximately 5%. CONCLUSION: At the 11 to 13(+6)-week scan, the measurement of fetal nuchal translucency and fetal heart rate and fetal examination for holoprosencephaly, exomphalos, and megacystis can identify >90% of fetuses with trisomy 13.
Abstract: OBJECTIVE: To study the effect of ethnic Chinese on the medians of free beta-hCG and PAPP-A in the first trimester of pregnancy. METHODS: The data of 943 women undergoing first trimester combined screening for fetal Down syndrome were analysed to derive the Chinese-specific medians. The calculated risk of Down syndrome based on these Chinese-specific medians was compared with that based on the original algorithm of the Fetal Medicine Foundation (FMF). RESULTS: The maternal serum levels of multiples of median of free beta-hCG and PAPP-A were significantly higher among the Chinese than among the Caucasians. The weight-adjusted gestation-specific medians were developed. Without adjustment for ethnicity, the original FMF algorithm underestimated the risk of Down syndrome by a median of 1%. Adjustment by ethnicity increased the false-positive rate by 10% (from 5.3 to 5.9%). CONCLUSION: Ethnic Chinese have a significantly higher maternal serum level of free beta-hCG and PAPP-A in the first trimester, which could not be explained by differences in maternal weight. Adjustment for ethnicity may be necessary for these biochemical markers in a first trimester screening program.
Abstract: This paper explores the meaning of higher risk status to women undergoing prenatal maternal screening for chromosomal anomalies. Quotations from lightly structured interviews and transcripts of pre-screening consultations in suburban London are used to illustrate pregnant women's diverse responses to the offer of screening, and to entering, living with and exiting from higher risk status. Some women reject screening in order to avoid the psychosocial and medical risks associated with higher risk status, or because they rule out pregnancy termination. They may question the risk selection implicitly built into the provision of preventative systems for some health problems but not others. Women who screen at higher risk may challenge this designation by questioning the system-specific probability used to separate them from the lower risk population. However, some experience distress even when they appreciate the precautionary basis on which their higher risk designation is based. They may find disengagement from higher risk status difficult after a diagnostic test has ruled out chromosomal anomalies. The findings highlight the complexity of communicating risk information to pregnant women and other screened populations, and emphasise the need to support those living with higher risk status and the benefits of keeping the time lived with this status as short as possible.
Abstract: OBJECTIVE: To investigate the potential value of combining uterine artery Doppler ultrasonography with the measurement of maternal serum pregnancy-associated plasma protein-A (PAPP-A), free beta-human chorionic gonadotropin (beta-hCG), activin A and inhibin A at 22 + 0 to 24 + 6 weeks' gestation, in the prediction of pregnancies that subsequently develop pre-eclampsia. METHODS: The maternal serum PAPP-A, free beta-hCG, activin A and inhibin A concentrations at 22 + 0 to 24 + 6 weeks' gestation were measured in samples obtained from women with singleton pregnancies who participated in a screening study for pre-eclampsia by transvaginal color flow Doppler measurement of the uterine artery pulsatility index (PI). A search was made of the database to identify those who subsequently developed pre-eclampsia (n = 24) and a group of controls with normal outcome (n = 144). Regression analysis was performed to establish any relationship between the biochemical markers themselves and between the biochemical markers and uterine artery mean PI. A multivariate Gaussian model combining various biochemical markers with uterine artery mean PI was developed using standard statistical modeling techniques and the performance of such models in discriminating cases with pre-eclampsia was evaluated by receiver-operating characteristics curve (ROC) analysis. RESULTS: In the pre-eclampsia group, compared to the controls, the uterine artery mean PI and the maternal serum levels of PAPP-A, free beta-hCG, activin A and inhibin A were significantly increased. The predicted detection rates of pre-eclampsia, for a false positive rate of 5%, was 50% by uterine artery mean PI, 5% by PAPP-A, 10% by free beta-hCG, 35% by inhibin A and 44% by activin A. Screening by a combination of uterine artery mean PI and maternal serum activin A and inhibin A could detect 75% and 92% of patients who subsequently developed pre-eclampsia, for false positive rates of 5% and 10%, respectively. CONCLUSION: Screening for pre-eclampsia by uterine artery PI at 22 + 0 to 24 + 6 weeks' gestation can be improved by measurement of activin A and inhibin A levels.
Abstract: OBJECTIVE: To examine whether in pregnancies with fetal trisomy 21 the level of maternal serum free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11 + 0 to 13 + 6 weeks' gestation is independent of the presence or absence of tricuspid regurgitation and to estimate the performance of a screening test that combines tricuspid regurgitation with fetal nuchal translucency (NT) thickness and serum free beta-hCG and PAPP-A. METHODS: The study population comprised 77 trisomy 21 and 232 chromosomally normal fetuses from singleton pregnancies at 11 + 0 to 13 + 6 weeks of gestation. In all cases the fetal karyotype was determined by chorionic villus sampling (CVS), which was carried out at the request of the parents after first-trimester screening for trisomy 21 by fetal NT and maternal serum free beta-hCG and PAPP-A. Immediately before chorionic villus sampling, fetal echocardiography was performed and the presence or absence of tricuspid regurgitation was determined by pulsed wave Doppler ultrasonography.The distribution of fetal NT, maternal serum free beta-hCG and PAPP-A in trisomy 21 fetuses with absent and present tricuspid regurgitation was examined. We examined two screening strategies: first, integrated first-trimester screening in all patients and second, first-stage screening of all patients using fetal NT and maternal serum free beta-hCG and PAPP-A followed by second-stage assessment of tricuspid regurgitation only in those with an intermediate risk of 1 in 101 to 1 in 1000 after the first stage. RESULTS: Tricuspid regurgitation was observed in 57 (74.0%) of the trisomy 21 fetuses and in 16 (6.9%) of the chromosomally normal fetuses. There were no significant differences in median maternal age, median gestational age, free beta-hCG multiples of the median (MoM) and PAPP-A MoM in trisomy 21 fetuses with and without tricuspid regurgitation. The modeled detection rates of trisomy 21 for fixed false positive rates of 1%, 2% and 5% in screening by maternal age, fetal NT thickness and maternal serum free beta-hCG and PAPP-A and assessment of tricuspid flow in all cases were 87%, 90% and 95%. In the two-stage approach, the estimated detection rate was 91% and the false positive rate was 2.6%. CONCLUSIONS: There is no relationship between tricuspid regurgitation and the levels of maternal serum free beta-hCG and PAPP-A in cases with trisomy 21. An integrated sonographic and biochemical test at 11 + 0 to 13 + 6 weeks can potentially identify about 90% of trisomy 21 fetuses for a false-positive rate of 2-3%.
Abstract: OBJECTIVES: ADAM12-s is a placental protein. In early pregnancy, reduced maternal levels of ADAM12-s have been reported in association with foetal trisomy 21 or 18 and in cases that subsequently develop pre-eclampsia and foetal growth restriction. The aim of this study is to investigate the distribution of ADAM12-s in early pregnancy by comparing its concentration in maternal serum, amniotic fluid and coelomic fluid. METHODS: Coelomic fluid was obtained by coelocentesis from 13 singleton pregnancies with live foetuses at 6.9-9.3 weeks of gestation. Maternal serum was also obtained in all cases and in six cases amniotic fluid was also obtained. The concentration of ADAM12-s was measured by dissociation enhanced lanthanide fluoro-immunoassay. RESULTS: The median concentration of ADAM12-s in maternal serum was 132.7 (range 33.8-254.5) ng/mL and in coelomic fluid it was 10.5 (range 1.3-15.8) ng/mL; there were no detectable levels in five of the six amniotic fluid samples. The concentration of maternal serum ADAM12-s increased significantly with gestation (r = 0.862, p < 0.0001). There was no significant association between coelomic fluid ADAM12-s and either gestation (r = 0.255, p = 0.401) or maternal serum ADAM12-s (r = 0.302, p = 0.316). CONCLUSION: The distribution of ADAM12-s in maternal serum and the early embryonic fluid compartments is consistent with its syncytiotrophoblastic origin.
Abstract: OBJECTIVES: To examine the clinical utility of the first-trimester markers of aneuploidy in their ability to predict future fetal loss. METHODS: We examined 54,722 singleton pregnancies with no chromosomal abnormality and with complete outcome data that had undergone screening for trisomy 21 by a combination of fetal nuchal translucency (NT) thickness, maternal serum free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11 + 0 and 13 + 6 weeks' gestation. The biochemical markers were converted to multiples of the expected normal median for a pregnancy of the same gestation (MoM) and the measurements of fetal NT were expressed as the difference (delta) from the normal median NT for crown-rump length (CRL). The association between free beta-hCG, PAPP-A and delta NT and the incidence of fetal loss prior to 24 weeks, at or after 24 weeks or at any time, was assessed by comparing the relative incidence at a number of MoM or delta NT cut-offs and at various centile cut-offs. At various marker levels the likelihood ratio (LR) for fetal loss was also calculated. RESULTS: The rate of fetal loss increased with decreasing maternal serum free beta-hCG and PAPP-A and increasing delta NT. At the 5th centile of the normal outcome group for free beta-hCG (0.41 MoM) the odds ratio for fetal loss before 24 weeks, at or above 24 weeks and at any gestation was 3.1, 1.8 and 2.6, respectively. The respective values for the 5th centile of PAPP-A (0.415 MoM) were 3.3, 1.9 and 2.8 and for the 95th centile of delta NT they were 2.5, 1.9 and 2.2, respectively. There was almost no correlation between reduced levels (<or=0.50 MoM) of PAPP-A and reduced levels of free beta-hCG in either the normal pregnancy group (r = 0.041) or the group with fetal death (r = 0.072), indicating relatively independent prediction by either biochemical marker. CONCLUSIONS: Low levels of maternal serum PAPP-A and free beta-hCG and increased fetal NT are associated, in the absence of an abnormal karyotype, with an increased risk of impending fetal death. The likelihood ratio profiles provided at various levels of PAPP-A or free beta-hCG may be of some help in counseling women with such results and raise awareness among health-care professionals for increased surveillance in such cases.
Abstract: BACKGROUND: A Disintegrin And Metalloprotease 12 (ADAM 12) is a glycoprotein synthesised by placenta and it has been shown to be a potential first-trimester maternal serum marker for Down syndrome (DS) in two small series. Here we analyse further, the potential of ADAM 12 as a marker for DS in a large collection of first-trimester serum samples. MATERIALS AND METHODS: The concentration of ADAM 12 was determined in 10-14-week pregnancy sera from 218 DS pregnancies and 389 gestational age-matched control pregnancies, which had been collected as part of routine prospective first-trimester screening programs (DS = 105) or as part of previous research studies (DS = 113). ADAM 12 was measured using a semi-automated time resolved immunofluorometric assay and median values for normal pregnancies were established by polynomial regression. These medians were then used to determine population distribution parameters for DS and normal pregnancy groups. Correlation with previously established PAPP-A and free beta-hCG multiple of the medians (MoMs) and delta nuchal translucency (NT) were determined and used to model the performance of first-trimester screening with ADAM 12 in combination with other first-trimester markers at various time periods across the first trimester. The benefits of a contingent testing model incorporating early measurement of PAPP-A and ADAM 12 were also explored. RESULTS: The maternal serum concentration of ADAM 12 was significantly reduced (p = 0.0049) with an overall median MoM of 0.79 in the DS cases and a log(10) MoM SD of 0.3734 in the DS cases and 0.3353 in the controls. There was a significant correlation of ADAM 12 MoM in DS cases with gestational age (r = 0.375) and the median MoM increased from 0.50 at 10-11 weeks to 1.38 at 13 weeks. ADAM 12 was correlated with maternal weight (r(controls) = 0.283), PAPP-A (r(controls) = 0.324, r(DS) = 0.251) but less so with free beta-hCG (r(controls) = 0.062, r(DS) = 0.049) and delta NT (r(controls) = 0.110, r(DS) = 0.151). ADAM 12 was significantly (p = 0.026) lower in smokers (0.87 vs 1.00) and elevated in Afro-Caribbean women compared to Caucasian women (1.34 vs 1.00).Population modelling using parameters from this and an earlier study showed that a combination of ADAM 12 and PAPP-A measured at 8-9 weeks and combined with NT and free beta-hCG measured at 12 weeks could achieve a detection rate of 97% at a 5% false-positive rate or 89% at a 1% false-positive rate. PAPP-A and ADAM 12 alone at 8-9 weeks could identify 91% of cases at a 5% false-positive rate. Using this as part of a contingent-screening model to select an intermediate risk group of women for NT and free beta-hCG at 11-12 weeks would enable the detection of 92% of cases with a 1% false-positive rate at a cost of providing NT and free beta-hCG for 6% of women with 94% of women having completed screening by the 10th week of pregnancy. CONCLUSION: ADAM 12 in early first trimester is a very efficient marker of DS. In combination with existing markers, it offers enhanced screening efficiency in a two-stage sequential first-trimester screening program or in a contingent-screening model, which may have benefits in health economies where universal access to high quality ultrasound is difficult. More data on early first-trimester cases with DS are required to establish more secure population parameters by which to assess further the validity of these models.
Abstract: BACKGROUND: Recent NICE Guidelines have emphasized the need to have in place by 2007 the capability of offering screening to all women in the first trimester using a combination of maternal age with the ultrasound marker nuchal translucency thickness (NT) and the maternal serum biochemical markers free beta-hCG and pregnancy-associated plasma protein-A (PAPP-A). Laboratories will therefore need to consider how to introduce the biochemical component of screening. With the recent launch of these assays on the DPC Immulite 2000 platform, it is appropriate and timely to investigate their clinical and analytical performance on a high throughput immunoassay analyser. METHODS: Within-run and between-day precision was assessed in the normal way. Bias was assessed by comparing samples from normal pregnancies (n=813) and pregnancies with Down's syndrome (n=60) run on both the DPC system and our routine Kryptor system. Gestational day-specific medians for each marker were calculated from the unaffected population. Mathematical modelling was used to predict the clinical performance of the two markers. RESULTS: The within-run coefficient of variation (CV) was around 3.5% and between-day CV was around 6-8% for both assays. Comparison with EQA samples showed a 2% positive bias against the ALTM for free beta-hCG and a 21% positive bias for PAPP-A, which reduced to 11% when compared with the Kryptor method mean. When compared with the Kryptor, the DPC free beta-hCG showed a significant concentration-related negative bias above concentrations of 50 IU/L in both unaffected and affected pregnancy samples. After conversion to MoM in the Down's syndrome group, the DPC free beta-hCG assay showed a MoM-related bias at higher MoM values. For PAPP-A a positive MoM-related bias was also evident. In cases with Down's syndrome, the median free beta-hCG MoM was 1.703 for DPC and 1.698 by the Kryptor, which was not significantly different. For PAPP-A, the median MoM was 0.62 for DPC and 0.47 by the Kryptor, which was significantly (P=0.025) different. This difference, if real, is likely to result in a lower detection of cases with Down's syndrome. Statistical modelling techniques suggest that this would be 58% compared with the expected 67% when combined with maternal age and free beta-hCG. When combined with NT, however, this would be reduced to 85% compared with the 90% expected. CONCLUSIONS: While laboratories may find some organizational benefit from running first trimester Down's syndrome screening on such routine high-throughput immunoassay analysers, better clinical performance is likely to be achieved with alternative platforms to the DPC Immulite 2000.
Abstract: OBJECTIVE: To evaluate the influence of maternal insulin dependent diabetes mellitus (IDDM) on maternal serum free beta-hCG, PAPP-A and fetal nuchal translucency (NT), thickness at 11 to 13(+6) weeks of gestation in a large cohort of women screened prospectively for chromosomal anomalies. METHODS: Information on maternal IDDM status, maternal serum biochemical marker levels and fetal NT were collected from the prenatal screening computer records in two first-trimester screening centres. In total the control group included 33 301 pregnancies of which 16 366 had NT and maternal serum biochemistry results and 16 305 with NT only. The IDDM group included 195 pregnancies of which 79 had NT and maternal serum biochemistry results and 127 with NT only. The median maternal weight corrected free beta-hCG and PAPP-A, expressed as multiple of the median (MoM), and fetal NT, expressed as delta values, in the IDDM and non-IDDM groups were compared. RESULTS: There were no significant differences between the IDDM and non-IDDM groups in median maternal weight corrected free beta-hCG (IDDM 0.87 MoM, 95% Confidence Interval 0.75 to 1.16 MoM, non-IDDM 1.00 MoM), median maternal weight corrected PAPP-A (IDDM 1.02 MoM, 95% Confidence Interval 0.83 to 1.05 MoM, non-IDDM 1.01 MoM), or mean delta NT (IDDM 0.0358 mm, non-IDDM 0.0002 mm). CONCLUSIONS: In pregnancies with maternal IDDM, first-trimester screening for chromosomal defects does not require adjustments for the measured fetal NT. However, more data are required before the possible reduction in maternal serum free beta-hCG and the reduction of PAPP-A suggested by the published world series can be considered sufficiently important to take into account in the calculation of risks for chromosomal defects.
Abstract: BACKGROUND: Previous studies have shown an association between low first trimester maternal serum free beta-hCG and PAPP-A and subsequent development of pregnancy complications. Similarly, uterine artery Doppler in the late second trimester has shown that high impedance to flow is associated with increased risk for preeclampsia and fetal growth restriction. The objective of this study is to determine whether there is an association between the maternal serum concentration of PAPP-A and free beta-hCG at 11-13(+6) weeks with the uterine artery pulsatility index (PI) at 22-24 weeks, and secondly, to compare the screening characteristics of the two methods in the prediction of adverse pregnancy outcome. METHODS: Maternal serum PAPP-A and free beta-hCG at 11-13(+6) weeks and uterine artery PI at 22-24 weeks were measured in 4390 women with singleton pregnancies. Pregnancies with chromosomal defects or fetal anomalies were excluded. The biochemical and Doppler measurements were compared between those with normal outcome and those resulting in spontaneous preterm delivery, pre-eclampsia and fetal growth restriction (FGR). Detection rates using a combination of the biochemical and Doppler measurements were investigated. RESULTS: In the pregnancies resulting in pre-eclampsia (n = 64) and FGR (n = 172), the median PAPP-A was lower (0.844 and 0.813 MoM), the median uterine artery mean PI was higher (1.56 and 1.18) but the median free betahCG was not significantly different (0.923 and 0.933 MoM) than in the normal outcome group. In the preterm delivery group (n = 159), the median free beta-hCG (0.944 MoM) and uterine artery mean PI (1.06) were not significantly different from normal but the median PAPP-A (0.928 MoM) was significantly lower than normal. In screening for pre-eclampsia, the detection rate, for a 5% false-positive rate, was 14.1% for PAPP-A, 54.7% for uterine artery mean PI and 62.1% for a combination of PAPP-A and uterine artery mean PI. CONCLUSION: Maternal serum PAPP-A at 11-13(+6) of gestation is significantly lower in adverse pregnancy outcomes. The combination of first trimester serum PAPP-A and uterine artery mean PI at 22-24 weeks improves the screening efficacy for the prediction of pre-eclampsia.
Abstract: OBJECTIVE: Investigation of the possible role of leptin in early pregnancy failure. METHODS: Leptin concentration was measured in maternal serum, coelomic fluid and amniotic fluid from 15 singleton pregnancies with live fetuses and 7 missed miscarriages at 7-10 weeks of gestation. RESULTS: In the pregnancies with live fetuses, the median leptin concentration was significantly higher in coelomic fluid (median 33.1 ng/ml) than in maternal serum (median 8.1 ng/ml) or amniotic fluid (median 0.5 ng/ml). In the pregnancies with missed miscarriage, compared to those with live fetuses, the median leptin concentration in coelomic fluid was higher (median 45.3 ng/ml), but in maternal serum it was not significantly different (median 5.5 ng/ml). CONCLUSIONS: The high coelomic fluid leptin concentration suggests that embryonic death may be preceded by impaired oxygenation of the placenta that stimulates production of leptin.
Abstract: BACKGROUND: Screening for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free beta-hCG and pregnancy associated plasma protein-A (PAPP-A) at 11-13(+6) weeks of gestation is associated with a detection rate of 90%, for a false-positive rate of 5%. Recent evidence suggests that in about 70% of fetuses with trisomy 21 the nasal bone is not visible at the 11-13(+6) week scan and that the frequency of absence of nasal bone differs in different ethnic groups. In addition, there is a relationship between absent nasal bone and nuchal translucency thickness. In a preliminary study we showed that while PAPP-A levels were lower and free beta-hCG levels were higher in trisomy 21 fetuses with an absent nasal bone, this difference was not statistically different. In fetuses with trisomy 13 and trisomy 18, there is also a high (57 and 67%) incidence of an absent nasal bone. The aim of this present study was to extend our examination of whether the level of maternal serum biochemical markers is independent of the presence or absence of the nasal bone in cases with trisomy 21 and to ascertain if any differences exist in cases with trisomies 13 and 18. METHODS: This study data comprised 100 trisomy 21 singleton pregnancies at 11-13(+6) weeks of gestation from our previous study and an additional 42 cases analysed as part of routine OSCAR screening. A total of 34 cases with trisomy 18 and 12 cases with trisomy 13 were also available. Ultrasound examination was carried out for measurement of fetal NT and assessment of the presence or absence of the fetal nasal bone. Maternal serum free beta-hCG and PAPP-A were measured using the Kryptor rapid random access immunoassay analyser (Brahms Diagnostica AG, Berlin). The distribution of maternal serum free beta-hCG and PAPP-A in chromosomally abnormal fetuses with absent and present nasal bone was examined. RESULTS: The nasal bone was absent in 29 and present in 13 of the new trisomy 21 cases and in 98 (69%) and 44 respectively in the combined series. For the trisomy 18 cases, the nasal bone was absent in 19 (55.9%) cases and in 3 (25%) of cases of trisomy 13. There were no significant differences in median maternal age, median gestational age, NT delta, free beta-hCG MoM and PAPP-A MoM in trisomy 21 fetuses with and without a visible nasal bone, and similarly for those with trisomies 13 or 18. For a false-positive rate of 5%, it was estimated that screening with the four markers in combination with maternal age would be associated with a detection rate of 96% of cases with trisomy 21. For a false-positive rate of 0.5%, the detection rate was 88%. CONCLUSIONS: There is no relationship between an absent fetal nasal bone and the levels of maternal serum PAPP-A or free beta-hCG in cases with trisomies 13, 18 or 21. An integrated sonographic and biochemical test at 11-13(+6) weeks can potentially identify about 88% of trisomy 21 fetuses for a false-positive rate of 0.5%.
Abstract: OBJECTIVE: To investigate whether first trimester maternal serum sex hormone-binding globulin (SHBG) concentrations are altered in women who subsequently develop preeclampsia or other pregnancy complications. POPULATION: Women undergoing first trimester combined ultrasound and biochemical screening for chromosomal anomalies. We searched the database and identified 32 pregnancies resulting in miscarriage, 64 pregnancies with preexisting or gestational diabetes mellitus, 107 with fetal growth restriction, 103 with preeclampsia, 64 with pregnancy-induced hypertension, and 26 with spontaneous preterm delivery. We also selected 400 controls from among the population of pregnancies that had a delivery of a normal baby with no pregnancy complications. METHODS: Maternal serum SHBG concentrations were measured retrospectively using a competitive chemiluminescent immunoassay. The levels between those with normal outcome and those resulting in adverse outcome were compared. RESULTS: The median maternal serum SHBG concentration was not significantly different from controls, in those that subsequently developed preeclampsia (median MoM 1.05), non-proteinuric hypertension (median MoM 0.94) or preterm delivery (median MoM 1.15). The levels were significantly lower in those with diabetes (median MoM, 0.81 p=0.0005) and those pregnancies resulting in miscarriage (median MoM 0.80, p=0.008). CONCLUSION: First trimester maternal serum SHBG concentrations are no different from controls in women who subsequently develop preeclampsia, pregnancy-induced hypertension, fetal growth restriction, or preterm delivery. Levels are reduced in those who subsequently miscarry or in those presenting with diabetes.
Abstract: OBJECTIVE: To evaluate a previous hypothesis that maternal serum biochemical markers used in the assessment of Down syndrome risk are related to maternal haemoglobin concentrations. METHODS: A series of 1306 second-trimester prenatal screening records were retrieved including information on marker levels (AFP and fbetahCG MoMs), Down's risk, a priori age risk, maternal weight and maternal height. Each individual record was merged with data from haematological investigations on samples collected on the same day. A similar series of 1688 first-trimester screening records were also retrieved including the maker levels for PAPP-A, and fbetahCG MoMs were merged with data from haematological investigations carried out on the same day. The two groups were categorised according to their haemoglobin levels; anaemic (less than 11.0 g/dL in first trimester and 10.5 g/dL in the second trimester), high haemoglobin (greater than 14.0 g/dL and 13.2 g/dL) or normal (between these ranges). An analysis was made of marker levels in the various groups before and after correction for ethnicity and of the screen-positive rate in the various groups. Using a formula based on maternal height and weight, variation of marker levels with plasma volume was assessed. RESULTS: In the first trimester, 12.6% of the pregnant population was anaemic and 1.6% had elevated haemoglobin levels. In the second trimester this was 12.7 and 3.9%. These figures varied considerably with ethnic origin, with Asian and Afro-Caribbean women being more anaemic than Caucasian women. Haemoglobin levels declined by 7% between the 11- and 21-week period. Maternal plasma volume (as calculated by a widely used maternal height and weight relationship) was not correlated with weight-corrected biochemical marker MoMs in either trimester. A weak but significant correlation of maternal plasma volume and haemoglobin concentration was observed. There was no significant correlation between biochemical marker MoMs and haemoglobin concentration. Although the proportion of pregnancies designated screen positive decreased as haemoglobin levels increased, this was paralleled by a decrease in the maternal age a priori risk. CONCLUSIONS: There is no relationship between maternal haemoglobin levels and the levels of Down syndrome markers in either the first or second trimester. Biochemical marker levels do not need to be corrected for haemoglobin concentrations when used in screening for Down syndrome.
Abstract: OBJECTIVE: This study was undertaken to evaluate the performance of a 1-stop clinic for first-trimester assessment of risk (OSCAR) for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness, and maternal serum-free ss- human chorionic gonadotrophin (hCG) and pregnancy-associated plasma protein-A (PAPP-A). STUDY DESIGN: OSCAR was carried out in 30,564 pregnancies at 11 to 13 + 6 weeks. Patient-specific risks for trisomy 21 and detection and false-positive rates were calculated. RESULTS: The median maternal age was 34 (range 15-49) years. Chromosomal abnormalities were identified in 330 pregnancies, including 196 cases of trisomy 21. The estimated risk for trisomy 21 was 1 in 300 or greater in 7.5% of the normal pregnancies, in 93.4% of those with trisomy 21 and in 88.8% of those with other chromosomal defects. CONCLUSION: The most effective method of screening for chromosomal defects is by first-trimester fetal NT and maternal serum biochemistry.
Abstract: The implementation of innovative medical technologies can raise unprecedented ethical, legal and social dilemmas. This is particularly so in the area of antenatal screening, which is dominated by the language of risk and probabilities. Second trimester serum screening for Down's syndrome and neural tube defects has a well-established place in antenatal care. Increasingly, first trimester screening with biochemical and ultrasound markers is being proposed as advance on this, yielding higher detection rates of Down's syndrome at an earlier gestational age. This article explores the experiences of 14 women offered innovative first trimester screening, which takes place within the context of a detailed ultrasound scan. The study is set within the UK, where recent policy changes mean that the offer of screening for fetal anomalies, particularly Down's syndrome, will become a routine part of antenatal care and offered to all pregnant women. This paper focuses on the significance of the scan in first trimester screening, and some of the potential dilemmas for women that can result from this. It then discusses the ways in which women made their decisions about screening, in particular, their work as 'moral pioneers'. We found that the part played by the ultrasound scan in first trimester screening, particularly in relation to the higher-quality images now being obtained, has the potential to introduce new and novel ethical dilemmas for pregnant women. Although concerns have been raised about pregnant women viewing ultrasound scans as benign, many of the women reported having thought carefully through their own moral beliefs and values prior to screening. It seems that whatever other implications they may have, first trimester screening technologies will continue the tradition of pregnant women acting as 'moral pioneers' in increasingly complex settings.
Abstract: OBJECTIVES: To evaluate the performance of first-trimester screening for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) and maternal serum free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A). In addition, the potential impact of a new individual risk-orientated two-stage approach to first-trimester screening was examined. METHODS: First-trimester combined screening for trisomy 21 was carried out in 75 821 singleton pregnancies with live fetuses at 11 + 0 to 13 + 6 gestational weeks. The detection and false-positive rates for different risk cut-offs were calculated. To examine the potential impact of an individual risk-orientated two-stage approach to first-trimester screening it was assumed that, after first-trimester combined screening, chorionic villus sampling (CVS) would be performed in all patients with a risk estimate of 1 in 100 or more and in none of those with a risk estimate of less than 1 in 1000. Those in the intermediate-risk category, with a risk estimate of between 1 in 101 and 1 in 1000, would have further assessment of risk by first-trimester ultrasound examination to determine presence/absence of the nasal bone, presence/absence of tricuspid regurgitation or normal/abnormal Doppler velocity waveform in the ductus venosus, and CVS would be performed if their adjusted risk became 1 in 100 or more. RESULTS: Fetal NT and maternal serum free beta-hCG and PAPP-A were successfully measured in all cases. The median maternal age was 31 (range, 13-49) years, the median gestation at screening was 12 (range, 11 + 0 to 13 + 6) weeks and the median fetal crown-rump length was 62 (range, 45-84) mm. Chromosomal abnormalities were identified in 544 pregnancies, including 325 cases of trisomy 21. The estimated risk for trisomy 21 was 1 in 300 or greater in 5.2% of normal pregnancies, in 92.6% of those with trisomy 21, in 88.5% of those with trisomy 18 or 13 and in 85.6% of those with other chromosomal defects. The detection rates for trisomy 21 were about 75% and 80% for respective false-positive rates of 1% and 2%. In the proposed individual risk-orientated two-stage screening for a risk cut-off of 1 in 100 the total false-positive rate would vary with the method used for the second stage of screening from 2.1% for absence of the nasal bone to 2.7% for increased impedance in the ductus venosus and 2.7% for tricuspid regurgitation and the respective detection rates would be 92.0%, 94.2% and 91.7%. CONCLUSIONS: First-trimester combined screening for trisomy 21 is associated with a detection rate of about 90% for a false-positive rate of 5%. Individual risk-orientated two-stage screening for trisomy 21 can potentially identify, in the first trimester of pregnancy, more than 90% of affected fetuses for a false-positive rate of 2-3%.
Abstract: OBJECTIVE: To examine the levels of free beta-human chorionic gonadotrophin (free beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) in second-trimester maternal serum from pregnancies affected by trisomy 13 and compare these with the known reduced levels of these markers in first-trimester cases in an attempt to better understand the pathophysiology of changes in marker levels in chromosomally abnormal pregnancies between the first and second trimester. METHODS: Using the Kryptor immunoassay system, we measured free beta-hCG and PAPP-A in 32 singleton pregnancies affected by trisomy 13 between 14 and 20 weeks of gestation. Using medians established in a previous study, these results were compared against 450 normal singleton pregnancies over the same gestational range. The data were combined with data from 82 cases of trisomy 13 previously examined in the first trimester (11-13 weeks) and an analysis of analyte trend was performed. RESULTS: The median free beta-hCG in multiples of the appropriate gestational median (MoM) in the second-trimester samples was not significantly different from the controls (1.15 (95% CI 0.827-1.651) vs 1.00). The median PAPP-A MoM in the second-trimester samples was significantly lower (p<0.001) than in controls (0.25 (95% CI 0.164-0.373) vs 1.00). Seventy-eight percent of cases were below the 5th centile of normal for PAPP-A. The combined cases in the first trimester had a median free beta-hCG MoM of 0.58 (95% CI 0.454-0.668) and a median PAPP-A MoM of 0.26 (95% CI 0.218-0.320). For PAPP-A, there was no significant change in median across the gestational period of 11 to 20 weeks, whilst for free beta-hCG, there was a significant increase with gestation (r=0.458, p<0.001). CONCLUSIONS: Although PAPP-A levels are reduced in trisomy 13 pregnancies in the second trimester, this isolated lower marker value is unlikely to be of value in screening for trisomy 13 in the second trimester. The aetiology of reduced levels of PAPP-A in cases with trisomy 13 may be similar to that in cases with trisomy 18, but different from that in cases with trisomy 21 since the temporal pattern in trisomies 13 and 18 are different from that in trisomy 21.
Abstract: OBJECTIVES: To assess whether there is a need to correct first-trimester biochemical markers (free beta-hCG and pregnancy-associated plasma protein-A (PAPP-A)) or first-trimester fetal nuchal translucency thickness (NT) in different ethnic groups, when screening for Downs syndrome at 11-14 weeks of gestation. METHODS: Free beta-hCG, PAPP-A and fetal NT were measured at 11-14 weeks of gestation in a group of women presenting for first-trimester screening in two OSCAR centres. The group comprised 61 219 sets of data from Caucasian women (the reference group); 4835 sets of data from South Asian women; 3450 sets of data from Oriental women and 2727 sets of data from Afro-Caribbean women. The Oriental data set was supplemented with a further 480 cases collected in Hong Kong and the Afro-Caribbean data set was supplemented with 216 cases collected from Kings College. The difference in marker values between the reference group and the other ethnic groups was compared before and after weight correction for the biochemical markers using standard statistical techniques. A correction factor for ethnic origin was applied for all three markers and the screen-positive rate before and after correction was assessed for the various groups. RESULTS: After maternal weight correction, in Afro-Caribbean women, the median PAPP-A was increased by 55% and the free beta-hCG increased by 11%. In south Asian women, the PAPP-A was increased by 8% and the free beta-hCG decreased by 7.5%. In Oriental women, the PAPP-A was increased by 9% and the free beta-hCG by 6%. For delta NT in Afro-Caribbean women, the values were 0.064 mm lower on average than in Caucasian women and for south Asian women 0.045 mm lower. The difference of -0.012 for Oriental women was not significant. Before correcting for ethnic origin, these changes resulted in the screen-positive rates being lower in the Afro-Caribbean group (3.7% vs 5.6%), the south Asian group (4.3% vs 5.6%) and Oriental group (4.9% vs 5.6%). After correction, the screen-positive rates were largely similar in the four groups. CONCLUSION: Differences in median PAPP-A, free beta-hCG and, to a lesser extent, in NT exist in Afro-Caribbean, South Asian and Oriental women. In populations where the medians and delta NT reference ranges are established in predominantly Caucasian populations, some correction for ethnicity is appropriate and can redress differences in screen-positive rates between these different groups.
Abstract: Human chorionic gonadotrophin (hCG) is released from placental trophoblasts and is involved in establishing pregnancy by maintaining progesterone secretion from the corpus luteum. Serum hCG is detected in the maternal circulation within the first 2-3 wks of gestation and peaks at the end of the first trimester before declining. In Down's syndrome (DS) pregnancies, serum hCG remains significantly high compared to gestation age-matched uncompromised pregnancies. It has been proposed that increased serum hCG levels could be due to transcriptional hyper-activation of the CGB (hCG beta) gene, or an increased half life of glycosylated hCG hormone, or both. Another possibility is that serum hCG levels remain high due to reduced availability of the hormone's cognate receptor, LHCGR, leading to lack of hormone utilization. We have tested this hypothesis by quantifying the expression of the hCG beta (CGB) RNA, LHCGR RNA and LHCGR proteins in chorionic villous samples. We demonstrate that chorionic expression of hCG beta (CGB) mRNA directly correlates with high serum hCG levels. The steady-state synthesis of LHCGR mRNA (exons 1-5) in DS pregnancies was significantly higher than that of controls, but the expression of full-length LHCGR mRNA (exons 1-11) in DS was comparable to that of uncompromised pregnancies. However, the synthesis of high molecular weight mature LHCGR proteins was significantly reduced in DS compared to uncompromised pregnancies, suggesting a lack of utilization of circulating hCG in DS pregnancies.
Abstract: BACKGROUND: In Down syndrome screening programmes, women with a previous affected pregnancy are assumed to have the same marker distribution as those without a family history. This assumption needs to be tested. METHODS: Information on previous aneuploidy pregnancies was routinely sought on the test request forms in three centres, Leeds, Romford and the Fetal Medicine Centre, London. For each woman with a previous aneuploidy (case), five unaffected pregnancies to women without a history were selected as controls. The markers tested included maternal serum free beta-human chorionic gonadotrophin (hCG), pregnancy-associated plasma protein A (PAPP-A), alpha-fetoprotein, unconjugated estriol and ultrasound nuchal translucency thickness. RESULTS: There were 375 cases: 303 with previous Down syndrome, 63 with Edwards syndrome and 9 with Patau's syndrome. There was a statistically significant difference between cases and controls, in the distribution of free beta-hCG and PAPP-A levels, adjusted for gestation. On average, free beta-hCG was increased by 10% in a subsequent pregnancy after aneuploidy (p < 0.005, Wilcoxon rank sum test) and for PAPP-A the increase was 15% (p < 0.0001). No other marker was significantly different. CONCLUSION: Risk calculation algorithms need to be modified to take account of the increased marker levels. Until data from sufficient affected pregnancies are available for study, it would be prudent to assume that the same increase as in unaffected pregnancies applies.
Abstract: OBJECTIVE: To investigate whether the reported increase in maternal serum activin A concentration in pre-eclampsia is evident from the first trimester. DESIGN: This was a case-control study carried out in antenatal clinics among singleton pregnancies at 10-14 weeks of gestation. METHODS: Activin A concentration was measured in stored maternal serum samples obtained at 11-14 weeks of gestation from 131 women who subsequently developed pre-eclampsia, 77 who developed non-proteinuric pregnancy-induced hypertension, 141 with fetal growth restriction in the absence of hypertensive complications and from 494 normotensive controls. RESULTS: Compared to the median activin A level in the control group (1.00 MoM), the median MoM in the patients who subsequently developed pre-eclampsia and pregnancy-induced hypertension (1.49 MoM and 1.32 MoM, respectively) was significantly increased (p < 0.001), and in patients with fetal growth restriction (1.02 MoM) it was not significantly different (p = 0.57). In the pre-eclampsia group (n = 131) the disease was considered to be sufficiently severe to necessitate iatrogenic delivery before 35 weeks in 25 patients, and in this group the median MoM was 1.92. CONCLUSION: Maternal serum activin A concentration at 12 weeks of gestation in pregnancies which subsequently develop hypertensive disease is increased, whereas in those complicated by fetal growth restriction it is normal.
Abstract: OBJECTIVE: To determine if maternal serum placental growth factor (PlGF) concentration at 11-14 weeks in pregnancies complicated by diabetes, including those with preexisting diabetes and those that developed gestational diabetes subsequently, differed from that in normal, uncomplicated pregnancies. STUDY DESIGN: PlGF concentration was measured in stored maternal serum samples obtained at 11-14 weeks of gestation from 82 women with diabetic pregnancies, including 32 with preexisting diabetes and 50 with gestational diabetes, and 400 normal controls. Gestational diabetes mellitus was diagnosed with the 75-g oral glucose tolerance test and by applying World Health Organization criteria. RESULTS: When expressed as the multiple of the median and adjusted for gestation, the log transformed values of PlGF were significantly higher (P < .05) in the diabetic group (mean multiple of the median, [MoM] 1.14; SD 0.11) as compared to the controls (mean MoM, 1.00; SD, 0.11). On further comparison between the diabetic groups with the controls, significant differences were found in the groups with gestational diabetes (mean MoM, 1.15; SD, 0.12) and non-insulin dependent diabetes (mean MoM, 1.16; SD, 0.09) but not in those complicated by insulin-dependent diabetes (mean MoM, 1.09; SD, 0.10). CONCLUSION: These findings suggest that in the first trimester of pregnancy the level of maternal PIGF was already significantly increased not only in pregnancies complicated by noninsulin dependent diabetes but also in those with gestational diabetes. The implications of these findings remain to be explored.
Abstract: OBJECTIVES: To evaluate the influence of cigarette smoking status on maternal serum free beta-hCG, PAPP-A and fetal nuchal translucency (NT) thickness at 11 to 14 weeks of gestation in a large cohort of women screened prospectively for chromosomal anomalies. METHODS: Information on maternal cigarette smoking status, maternal age, maternal serum biochemical marker levels and fetal NT were collected from the prenatal screening computer records in two OSCAR screening centres. Data was available from 32,730 unaffected pregnancies and from 124 with Down syndrome. Statistical analysis of the marker levels in the smoking and non-smoking group were carried out. The impact on false-positive rate of correcting for smoking status was assessed from a modelling exercise. RESULTS: Prevalence of smoking was significantly affected by maternal age with an overall incidence of 11.5%, which varied from 35% in women under 20 to 7% in women over 35. In the unaffected population, the median free beta-hCG MoM was significantly lower in the smoking group (0.97 vs 1.00) as was that for PAPP-A (0.84 vs 1.02). The standard deviation of the log(10) MoM free beta-hCG was lower in the smoking group and that for PAPP-A was higher in the smoking group. The difference in median marker levels did not seem to be related to the number of cigarettes smoked per day. In the group with Down syndrome, the median MoM free beta-hCG was not significantly different in the smokers (1.69 vs 1.86) as was that for PAPP-A (0.53 vs 0.57). Fetal delta NT was not significantly different in the unaffected smokers (0.11 vs 0.0 mm) or in those with Down syndrome (1.96 vs 2.25 mm). In the smoking group, when screening using maternal serum biochemistry and age alone, the false-positive rate was 6.17%, compared to 4.67% in an age-matched group of non-smokers. Correcting for smoking status by dividing the measured MoM by the median found in the smoking group resulted in the false-positive rate falling to 4.40%. When screening using NT, maternal serum biochemistry and age, the false-positive rate in smokers was 4.48%, which reduced to 3.46% after correction-in line with the 3.76% in the non-smoking group. The impact on detection rate was too small to be accurately measured. CONCLUSIONS: The impact of smoking on first-trimester biochemical marker levels does not seem to be dose related. Whilst correcting first-trimester biochemical markers for maternal smoking status has little impact at the population level for detection rates, a considerable reduction in false-positive rate can be achieved, reducing the level to that seen in non-smokers. However, the effect on the individual patient-specific risk can be substantial and could certainly make a difference to the patient's decision on whether to have an invasive test.
Abstract: OBJECTIVE: To ascertain, by means of a questionnaire, women's preferences for four different approaches to prenatal screening for Down syndrome. METHODS: Women attending antenatal clinics at six UK maternity units were asked to put in order of preference four different approaches to screening for Down syndrome all of which had the same false positive rate of 5%. The options were: (1) first-trimester testing, 90% detection of Down syndrome with results available in 1 h at one-stop clinics for the assessment of risk (OSCAR); (2) first-trimester testing, 90% detection and results available within 2-3 days (combined screening); (3) first-trimester testing plus second-trimester testing, 93% detection and results available within 2-3 days of second test (integrated testing); (4) second-trimester testing, 75% detection and results available within 2-3 days. RESULTS: Over 1100 women attending antenatal clinics at six maternity units across the UK returned the questionnaire. A total of 75% of women selected a first-trimester test (option 1 or option 2) as their first choice with 68.2% expressing a preference for the OSCAR approach and a further 6.8% for combined screening. Twenty-four percent of women opted for integrated testing as their first choice with only 1% expressing a preference for second-trimester screening. CONCLUSIONS: A first-trimester test is preferred by the majority of women over a test with marginally higher detection rate that delivers results later in pregnancy. Timing and rapid reporting of results appear to influence women's choice of test.
Abstract: OBJECTIVE: To investigate whether maternal plasma sex hormone-binding globulin (SHBG) concentrations are reduced in women who subsequently develop pre-eclampsia. METHODS: This was a cross-sectional study, carried out at antenatal clinics in seven hospitals in and around London. Healthy women underwent uterine artery Doppler velocimetry as a screening method for pre-eclampsia at 22-24 weeks of gestation. The first group (408 women) had normal uterine artery Doppler waveforms (mean uterine artery pulsatility index (PI) below 1.6). The second group (274 women) had increased impedance to flow in the uterine arteries (mean PI above the 95th centile, 1.6). Maternal plasma SHBG concentrations were measured retrospectively using a competitive chemiluminescent immunoassay. Pre-eclampsia was as defined by the International Society for the Study of Hypertension in Pregnancy. RESULTS: Plasma SHBG concentrations in the 80 (11.7%) women who subsequently developed pre-eclampsia were significantly lower than in the 585 (85.8%) women with normal pregnancy outcomes (median 336, range 142-674 nmol/l vs. median 336, range 142-674 nmol/l, p = 0.001). There was a strong correlation between SHBG concentrations and body mass index (r =-0.232246, p < 0.0001). There were no significant differences in maternal plasma SHBG concentrations in women with abnormal uterine artery Doppler (n = 274) compared with controls (n = 408) (median 324, range 101-635 nmol/l vs. median 336, range 142-674 nmol/l, p = 0.09). CONCLUSION: Maternal plasma SHBG concentrations are reduced in women who subsequently develop pre-eclampsia.
Abstract: OBJECTIVE: To describe and illustrate a method of setting Down syndrome screening targets and auditing performance that allows for differences in the maternal age distribution. METHODS: A reference population was determined from a Gaussian model of maternal age. Target detection and false-positive rates were determined by standard statistical modelling techniques, except that the reference population rather than an observed population was used. Second-trimester marker parameters were obtained for Down syndrome from a large meta-analysis, and for unaffected pregnancies from the combined results of more than 600,000 screens in five centres. Audited detection and false-positive rates were the weighted average of the rates in five broad age groups corrected for viability bias. Weights were based on the age distributions in the reference population. RESULTS: Maternal age was found to approximate reasonably well to a Gaussian distribution with mean 27 years and standard deviation 5.5 years. Depending on marker combination, the target detection rates were 59 to 64% and false-positive rate 4.2 to 5.4% for a 1 in 250 term cut-off; 65 to 68% and 6.1 to 7.3% for 1 in 270 at mid-trimester. Among the five centres, the audited detection rate ranged from 7% below target to 10% above target, with audited false-positive rates better than the target by 0.3 to 1.5%. CONCLUSION: Age-standardisation should help to improve screening quality by allowing for intrinsic differences between programmes, so that valid comparisons can be made.
Abstract: OBJECTIVE: To investigate whether mid-trimester maternal plasma homocysteine concentration is elevated in women who develop pre-eclampsia and in those women identified at high risk by abnormal uterine artery Doppler examination. METHODS: This was a multicenter study involving healthy women undergoing screening for pre-eclampsia by uterine artery Doppler velocimetry at 22-24 weeks' gestation. Abnormal uterine artery blood flow was defined as a mean pulsatility index (PI) above the 95th centile (1.6). Controls (mean PI < 1.6) were matched for gestational age and date of blood sample collection. Maternal plasma homocysteine concentration was measured retrospectively using a chemiluminescent immunoassay. RESULTS: In total, 683 women were recruited. Maternal plasma homocysteine concentration did not vary with gestation. Maternal plasma homocysteine concentration in women who subsequently developed pre-eclampsia (n = 80, 12%) was not significantly different from women with uncomplicated pregnancies (n = 536, 78%) (median 5.1, range 2.7-14.1 micromol/l vs. median 5.5, range 1.9-27.9 micromol/l, p = 0.44). There were no significant differences in the maternal plasma homocysteine concentration in women with abnormal uterine artery Doppler findings (n = 275) compared with controls (n = 408), (median 5.6, range 2.6-17.7 micromol/l vs. median 5.4, range 1.9-27.9 micromol/l, p = 0.13). CONCLUSION: Mid-trimester maternal plasma homocysteine concentration is not elevated in women who developed pre-eclampsia even in those at high risk defined by abnormal uterine artery Doppler velocimetry.
Abstract: OBJECTIVE: To find whether fbetahCG, PAPP-A and inhibin-A levels in maternal serum or fetal nuchal translucency (NT) thickness at the first-trimester screening for trisomy 21 (T21) might detect women at high risk for adverse pregnancy outcomes. METHODS: A retrospective analysis of 1136 women with singleton pregnancy between 10 and 14 weeks. Women with pregnancy complications were allotted to five subgroups: small for gestational age (SGA), large for gestational age (LGA), gestational diabetes (GDM), hypertensive disorders, preterm delivery; women with normal pregnancy represented the control group. NT, maternal serum fbetahCG, PAPP-A and inhibin-A were measured. Mann-Whitney test was used for the comparison of fbetahCG, PAPP-A, inhibin-A and NT between a subgroup of a certain pregnancy complication and the control group. Multivariate logistic regression models were built to explore the relationship among different variables and the occurrence of pregnancy complications. RESULTS: PAPP-A values were significantly lower in women who delivered SGA babies (n=51, 0.76 MoM; p=0.002) and significantly higher in women who delivered LGA babies (n=120, 1.12 MoM; p=0.036). In women with GDM (n=27), fbetahCG, PAPP-A and inhibin-A were insignificantly lower than in controls, whereas in women with hypertensive disorders (n=56) no significant differences between the groups were found. In women with a preterm delivery (<34 weeks) (n=17), inhibin-A levels were significantly higher (1.25 MoM; p=0.015). CONCLUSION: Low PAPP-A level is associated with the delivery of an SGA baby and high PAPP-A with the delivery of an LGA baby. High inhibin-A is associated with preterm delivery before 34 weeks. Feto-placental products in the first trimester do not prove to be useful as a screening tool for predicting pregnancy complications.
Abstract: OBJECTIVE: To assess the suitability of either the log-linear or reciprocal-linear regression procedure for maternal weight correction of biochemical marker MoMs in the first trimester. METHODS: Data from two prospective first-trimester OSCAR screening programmes including 32,010 women with first-trimester maternal serum-free beta-hCG and PAPP-A measured by the Kryptor analyser was analysed by regression analysis to provide parameters for the log-linear and reciprocal-linear MoM correction procedures. Assessment was made by goodness of fit to the data. The impact on detection rate and false-positive rate of the different correction procedures was assessed using statistical modelling with biochemical markers alone. RESULTS: Both log-linear and reciprocal-linear correction were shown to fit the data well. For free beta-hCG, the log-linear procedure was marginally superior to the reciprocal-linear procedure (r2=0.986 v 0.980), whilst for PAPP-A the reciprocal-linear procedure was marginally better (r2=0.991 v 0.985). Log-linear correction reduced the variance for both markers more than did the reciprocal-linear procedure. For free beta-hCG, the sd was reduced from 0.2675 to 0.2605 and for PAPP-A, it was reduced from 0.2545 to 0.2336. Correcting for maternal weight was shown to reduce the population false-positive rate from 7.0 to 6.5%, whilst maintaining the same detection rate at a risk cut-off of 1 in a 100. At individual levels, a two-fold variation in risk was demonstrated depending upon the individual's weight. CONCLUSIONS: To provide accurate individual patient-specific risks for trisomy 21, maternal weight must be taken into account and should be a mandatory data item for screening programmes. Maternal weight correction in the first trimester using free beta-hCG and PAPP-A can be best achieved using the log-linear procedure.
Abstract: OBJECTIVE: To assess whether in screening for trisomy 21 by nuchal translucency (NT) the delta or the multiples of the median (MoM) approach is the most appropriate method for calculating accurate individual patient-specific risks. METHODS: Data on fetal NT and crown-rump length from 128,030 unaffected and 428 trisomy 21 pregnancies, measured by sonographers who had obtained The Fetal Medicine Foundation Certificate of Competence in the 11-14-Week Scan, were used. We examined first, if the distribution of NT MoM and log(10)(NT MoM) was Gaussian; second, if the standard deviation of the distributions did not change with gestation; and third, if the median MoM in the affected population was a constant proportion of the median for unaffected pregnancies. All of these features are required to underpin the MoM approach. NT distributions and those of delta-NT were also analyzed. A non-parametric kernel density method was then used to assess the validity of both methods. Errors in the estimation of individual patient-specific risks using the MoM approach were assessed. RESULTS: In the unaffected pregnancies, the distributions of NT MoM and log(10)(NT MoM) were not Gaussian and the standard deviation of log(10)(NT MoM) decreased with gestation. In the trisomy 21 pregnancies, the median NT MoM decreased significantly with gestation, whereas the median delta-NT did not change with gestation. The non-parametric density approach showed that contours of constant likelihood ratio were parallel to the gestational age-dependent median NT values, thus supporting the delta-NT approach. The NT MoM approach resulted in women being given an overestimate of risk for trisomy at 11 weeks and a considerable underestimate of risk at 13 weeks. CONCLUSION: In the calculation of risk for trisomy 21 by NT the NT MoM approach is inaccurate and inappropriate because the underlying assumptions are not valid. In contrast, the delta-NT approach gives accurate estimates of risks.
Abstract: BACKGROUND: In a rapid point-of-care screening programme for chromosomal anomalies, analysis of biochemical markers in maternal blood can now be accomplished in a rapid time frame (less than 20 min). The need to leave whole blood samples some 10 min for coagulation and a further 5 min for centrifugation adds additional processing time. METHODS: The possibilities for reducing this processing time were investigated using various anticoagulated blood collection systems and the Kryptor analytical platform. Plasma levels of alpha-fetoprotein (AFP), pregnancy-associated plasma protein-A (PAPP-A) and free human chronic gonadotrophin beta-subunit (beta-hCG) were compared with those in maternal serum. RESULTS: From the mean results from ten patients it was shown that use of heparin plasma resulted in a statistically significant reduction in levels of PAPP-A and that EDTA plasma reduced the levels of PAPP-A dramatically. For AFP, levels in citrated plasma and EDTA plasma were also significantly reduced, whereas levels of free beta-hCG were not affected. CONCLUSION: Use of alternative sample types for PAPP-A is not possible. The sample of choice for first trimester screening using the Kryptor platform is maternal serum.
Abstract: OBJECTIVE: To evaluate the performance of screening for fetal trisomy 21 in the first trimester of twin pregnancies by a combination of maternal serum biochemistry and ultrasonography. DESIGN: Three year retrospective review of screening performance. SETTING: District General Hospital maternity unit. POPULATION: All women booked to receive routine antenatal care at Harold Wood Hospital between 1 June 1998 and 30th September 2001. The population included 13,940 women of all ages presenting with pregnancies between 10 weeks 3 days and 13 weeks 6 days gestation. Of these, 230 had a twin pregnancy. METHODS: Women booked into the clinic were offered screening using a combination of maternal serum free beta-hCG and pregnancy-associated plasma protein-A (PAPP-A) and fetal nuchal translucency thickness. Women at increased risk of carrying a fetus with trisomy 21 or trisomy 13/18 (>/=1 in 300 at sampling) were offered counselling and an invasive diagnostic procedure. Follow up of the outcome of all pregnancies was carried out. For women who on examination were at 14 weeks of gestation or greater, or for women presenting as late bookers beyond 14 weeks, screening was performed in the same time frame using only maternal serum free beta-hCG and alpha-fetoprotein. MAIN OUTCOME MEASURES: The first trimester detection rate for trisomy 21 and all aneuploides, false positive rate, uptake of screening, uptake of invasive testing in women identified at increased risk and fetal loss rates after invasive testing. RESULTS: Overall, 97.4% of the women with twins (224/230) accepted first trimester screening. The rate of detection of trisomy 21 was 75% (3/4). Fetal death at presentation was found in 3.4% of fetuses (16/460). Of women who accepted screening, 4.3% (10/230) presented too late for fetal nuchal translucency measurement and 10.0% of women (23/230) presented too early. A risk for trisomy 21 was calculated for each fetus based on the individual fetal nuchal translucency thickness and the maternal biochemistry. The false positive rate among those eligible for first trimester screening was 9.0% (19/206) of pregnancies and 6.9% of fetuses (28/412). Uptake of invasive testing was 59% (10/17) with chorionic villus sampling in eight cases and amniocentesis in two. No fetal loss occurred within 28 days of chorionic villus sampling and no loss occurred after amniocentesis. One case of trisomy 21 was identified for every three invasive procedures. CONCLUSIONS: First trimester screening for trisomy 21 in twin pregnancies is both theoretically possible and practically achievable using a combination of nuchal translucency thickness and maternal serum biochemistry. However, dilemmas for the mother and health professionals when both nuchal translucency thickness measurements are normal might suggest that greater reliance be placed on the nuchal translucency thickness risk alone when counselling women about invasive testing.
Abstract: BACKGROUND: Screening for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free beta-hCG and pregnancy-associated plasma protein-A (PAPP-A) at 11 to 14 weeks of gestation is associated with a detection rate of 90% for a false-positive rate of 5%. Recent evidence suggests that in about 70% of fetuses with trisomy 21, the nasal bone is not visible at the 11th- to 14th-week scan (Cicero et al., 2001). The aim of this study was to examine whether fetal NT thickness and the level of maternal serum biochemical markers is independent of the presence or absence of the nasal bone, and to estimate the performance of a screening test that integrates the two sonographic and the two biochemical markers. METHODS: This was a retrospective case-control study comprising 100 trisomy 21 and 400 chromosomally normal singleton pregnancies at 11 to 14 weeks of gestation. Ultrasound examination was carried out for measurement of fetal NT and assessment of the presence or absence of the fetal nasal bone. Maternal serum free beta-hCG and PAPP-A were measured using the Kryptor rapid random-access immunoassay analyser (Brahms Diagnostica GmbH, Berlin). The distribution of fetal NT, maternal serum free beta-hCG and PAPP-A in trisomy 21 fetuses with absent and present nasal bone was examined. RESULTS: The nasal bone was absent in 69 and present in 31 of the trisomy 21 fetuses. There were no significant differences in median maternal age, median gestational age, NT delta, free beta-hCG MoM and PAPP-A MoM in trisomy 21 fetuses with and without a visible nasal bone. For a false-positive rate of 5%, it was estimated that screening with the four markers in combination with maternal age would be associated with a detection rate of 97%. For a false-positive rate of 0.5%, the detection rate was 90.5%. CONCLUSIONS: An integrated sonographic and biochemical test at 11 to 14 weeks can potentially identify about 90% of trisomy 21 fetuses for a false-positive rate of 0.5%.
Abstract: A multicentre study was carried out to determine the frequency and clinical consequences of extremely high maternal serum pregnancy-associated plasma protein (PAPP)-A. There was a total of 79 pregnancies with PAPP-A exceeding 5.0 multiples of the gestation-specific median in a series of 46 776 pregnancies tested (0.2%) at the 7 collaborating centres. Five pregnancies were lost to follow-up, one miscarried and one with Noonan's syndrome was terminated. Of the remaining 72 that ended in a live birth, one infant had gastroschisis and five pregnancies had obstetric complications: pre-eclampsia, pregnancy-induced hypertension, gestational diabetes and two with growth retardation. Among women with high PAPP-A and no complications or adverse outcomes, there was no evidence of a substantial change in the levels of other Down syndrome markers or the extent of nuchal translucency. Three analytical methods were used to assay PAPP-A and yielded different frequencies of extremely high levels (0.05%, 0.4% and 0.6%) possibly owing to cross-reaction with another substance. We conclude that women with high PAPP-A can be reassured that there is no reason to suppose that the outcome of pregnancy will differ from those with normal levels, provided other markers are normal. If, as more centres move their Down syndrome screening practice to the first trimester, additional cases emerge with Noonan's syndrome or gastroschisis and raised PAPP-A, this advice will need to be modified.
Abstract: OBJECTIVE: Analysis of the levels of cell-free fetal and total DNA in serum of women carrying a male fetus affected by trisomy 21, and comparison of these levels with those in women carrying a normal male fetus. METHODS: DNA was extracted from archived second-trimester maternal serum samples collected as part of a prenatal screening program. A total of 10 cases with trisomy 21 male fetuses were compared with 10 controls (male fetuses) with samples matched for duration of storage and gestational age. Real-time quantitative PCR of the SRY and albumin genes was used to quantify fetal and total DNA respectively. RESULTS: The median fetal DNA level in the group of 10 pregnancies with trisomy 21 was 31.98 cell-equivalents per mL compared to 34.06 in the control group. The difference was not significant. The median total DNA level in women with a trisomy 21 fetus was significantly higher (P = 0.029) than that in controls (36 152.6 vs 5832.81 cell-equivalents per mL). CONCLUSIONS: Although we could not confirm previous studies of an increased amount of fetal DNA in pregnancies affected by trisomy 21, we did find increased levels of total DNA. The possible reasons for these observations are discussed with respect to previous findings. Larger studies are needed to elucidate the true value, if any, of measurement of fetal and total DNA in maternal serum in the context of prenatal screening for chromosomal abnormalities.
Abstract: BACKGROUND: In a previous study we examined the changes in the median multiple of the median (MoM) with gestation of free beta human chorionic gonadotrophin (F beta-hCG), total human chorionic gonadotrophin (ThCG), alpha-fetoprotein (AFP) and pregnancy-associated plasma protein A (PAPP-A) in a large series of Down's syndrome pregnancies. Results showed that there was a significant temporal variation of the MoM for each marker. In this paper, we assess the impact of this temporal shift on the estimation of patient-specific risks and the detection rates (DRs) for Down's syndrome pregnancies. METHODS: Individual patient-specific risks, DRs and false positive rates were estimated using statistical modelling techniques and computer simulations. The data for these simulations were the regressed mean log(10) analyte MoMs, marker standard deviations (as log(10) MoM) and correlation coefficients derived from the analysis of over 1000 cases of Down's syndrome and 150,000 unaffected pregnancies between 6 and 20 weeks of gestation reported in our previous study. Two models were compared: the classical constant median separation model, which assumes no variation in median shift with gestation (model 1), and a variable median separation model (model 2), which takes account of the changes in median shift with gestation as described in our previous study. RESULTS: When individual patient-specific risks calculated for various MoM values using model 1 were compared with those derived from model 2, considerable differences in risk estimates were observed for all marker combinations, particularly in the first trimester. Using a 1 in 250 cut-off risk, DRs at each gestation in the second trimester for the AFP+F beta-hCG combination were maximized at 14-17 weeks of gestation and were virtually identical at 63-65% for model 1 and model 2. A similar trend was observed for the AFP+ThCG combination, with an optimum gestational range of 15-18 weeks and DRs of 66-68%. In the first trimester, using a 1 in 250 cut-off risk, DRs were more variable with gestation for the prime marker combination of F beta-hCG+PAPP-A, varying from 73% at 8 weeks to 65% at 13 weeks with model 1 and from 75% to 66% with model 2. CONCLUSION: Risk algorithms should take into account temporal variation in marker MoMs in order to produce accurate patient-specific risks. This also helps to maximize DRs, particularly when samples are taken out with the optimal gestational range.
Abstract: AIM: To assess whether glycoform variants of human chorionic gonadotrophin (hCG) are present in altered concentrations in the maternal serum in pregnancies affected by Down syndrome. METHODS: In a series of 50 cases of pregnancies complicated by Down syndrome and 278 unaffected pregnancies, we have examined maternal serum levels of hCG glycoforms (GlyhCG) in samples collected in the second trimester (14 to 21 weeks) using a sialic acid binding lectin immunoassay. We have compared these levels with those of other second trimester serum markers (Free beta-hCG, alpha fetaprotein (AFP) and Total hCG) and modelled detection rates and false positive rates of various biochemical markers in conjunction with maternal age using a maternal age standardized population. RESULTS: Maternal serum GlyhCG in cases of Down syndrome was significantly elevated (Median MoM 1.81) with 15 of 50 (30%) cases above the 95th centile for unaffected pregnancies. Free beta-hCG was also elevated (Median MoM 2.16) with 18 of 50 (36%) cases above the 95th centile. AFP levels were reduced (Median MoM 0.75) with 9 of 50 (18%) cases below the 5th centile. Total hCG levels whilst elevated (Median MoM 1.88) had only 15 of 50 (30%) cases above the 95th centile. Maternal serum GlyhCG levels showed significant correlation with total hCG and free beta-hCG (r = 0.6880 and 0.6922) in the Down group but not with AFP (r = 0.1237). When GlyhCG was combined together with AFP and maternal age, at a 5% false positive rate, the modelled detection rate was 53%, some 13% lower than when free beta-hCG was used and some 7% lower than when total hCG was used. CONCLUSION: Maternal serum GlyhCG, as measured by the sialic acid-binding lectin immunoassay is unlikely to be of additional value when screening for Down syndrome in the second trimester.
Abstract: Over the past three years approximately 12 000 women have been screened in the first trimester through our OSCAR programme, which utilizes fetal NT and maternal serum free beta-hCG and PAPP-A. During this time 30 cases of Down syndrome were identified either prenatally or postnatally. Using an established procedure the accuracy of predicted risk for Down syndrome was assessed in a population of 30 cases of Down syndrome and 11 758 unaffected pregnancies. The correlation between predicted risk and prevalence of Down syndrome was very high (r=0.9995). It is concluded that risks produced by the Fetal Medicine Foundation combined risk algorithm agree very closely with Down syndrome prevalence and can be used with confidence when counselling women of their risk.
Abstract: OBJECTIVE: To evaluate the performance of a one-stop clinic for assessment of risk (OSCAR) for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free beta-human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11-14 weeks of gestation. METHOD: Screening for trisomy 21 was carried out by OSCAR in 15 030 singleton pregnancies with live fetuses at 11-14 weeks. The estimated risk for trisomy 21 was calculated, and the women were counseled regarding this risk and the option of invasive testing or expectant management. Follow-up of the outcome of all pregnancies was carried out. The detection and false-positive rates for different risk cut-offs were calculated. RESULTS: Fetal NT and maternal serum free beta-hCG and PAPP-A were successfully measured in all cases. Pregnancy outcome, including karyotype results or the birth of a phenotypically normal baby, was obtained from 14 383 cases. The median maternal age of these cases was 34 (range 15-49) years and in 6768 (47.1%) the age was 35 years or greater. The median gestation at screening was 12 (range 11-14) weeks and the median fetal crown-rump length was 64 (range 45-84) mm. The estimated risk for trisomy 21 based on maternal age, fetal NT and maternal serum free beta-hCG and PAPP-A was 1 in 300 or greater in 6.8% (967 of 14 240) normal pregnancies, in 91.5% (75 of 82) of those with trisomy 21 and in 88.5% (54 of 61) of those with other chromosomal defects. For a fixed false-positive rate of 5% the respective detection rates of screening for trisomy 21 by maternal age alone, maternal age and serum free beta-hCG and PAPP-A, maternal age and fetal NT, and by maternal age, fetal NT and maternal serum biochemistry were 30.5%, 59.8%, 79.3% and 90.2%, respectively. CONCLUSION: Screening for trisomy 21 by a combination of maternal age, fetal NT and maternal serum biochemistry at 11-14 weeks can be provided in an OSCAR setting and is associated with a detection rate of about 90% for a false-positive rate of 5%.
Abstract: In a series of 54 cases of pregnancies complicated by Down syndrome and 224 unaffected pregnancies we examined maternal serum levels of hyperglycosylated human chorionic gonadotrophin (HhCG) in samples collected in the first trimester (11-13 weeks) using a sialic acid-specific lectin immunoassay. We compared these levels with those of other potential first trimester serum markers [free beta-hCG, pregnancy-associated plasma protein A (PAPP-A) and total hCG (ThCG)] and modeled detection rates and false-positive rates of various biochemical markers in conjunction with fetal nuchal translucency (NT) and maternal age using an maternal age standardized population. Maternal serum HhCG in cases of Down syndrome were significantly elevated (median MoM 1.97) with 24/54 (44%) of cases above the 95th centile for unaffected pregnancies. Free beta-hCG was also elevated (median MoM 2.09) with 33% of cases above the 95th centile. PAPP-A levels were reduced (median MoM 0.47) with 38% below the 5th centile. ThCG levels, whilst elevated (median MoM 1.34), had only 20% of cases above the 95th centile. Maternal serum HhCG levels were not correlated with fetal NT but showed significant correlation with ThCG and free beta-hCG and with PAPP-A in the Down syndrome group (r=0.536). Maternal serum HhCG levels in cases with Down syndrome had a significant correlation with gestational age, increasing as the gestation increased. When HhCG was combined together with fetal NT, PAPP-A and maternal age, at a 5% false-positive rate the modeled detection rate was 83%, some 6% lower than when free beta-hCG was used and some 4% better than when ThCG was used. Maternal serum HhCG is unlikely to be of additional value when screening for Down syndrome in the first trimester.
Abstract: OBJECTIVES: To assess the level of correlation of first trimester biochemical and biophysical markers of Down syndrome between different pregnancies in the same individual. To assess the impact that between pregnancy biological variability has on the likelihood that women who are at increased risk in a first pregnancy being also at increased risk in a subsequent pregnancy. METHODS: During a three period women attending the OSCAR clinic at Harold Wood Hospital have had the opportunity to have first trimester screening for Down syndrome and other aneuploidies using the maternal serum biochemical markers free beta-human chorionic gonadotrophin (hCG) and pregnancy associated plasma protein-A (PAPP-A) in conjunction with fetal nuchal translucency (NT) thickness and maternal age. Of the 111,105 women undergoing such screening, the computer records were examined for women who had more than one pregnancy. The results from 1002 women with two normal singleton pregnancies were available for analysis. Marker correlations (as MoM) were established between the pregnancies and the proportion of women likely to be at increased risk in each pregnancy estimated, as was the likelihood of women being at increased risk in both pregnancies. RESULTS: For fetal NT there was no correlation between NT MoM in the first and second pregnancy (r = 0.0959, p > 0.10). For maternal serum free beta-hCG MoM a significant correlation was found (r = 0.3976, p < 0.001), as was also found for PAPP-A MoM (r = 0.4371, p < 0.001). CONCLUSION: The implication for such between pregnancy marker association is that women who have an increased risk of Down syndrome in one pregnancy are two or three times more likely to repeat this event in their next pregnancy. This information may be useful in counselling women when undergoing first trimester screening in a subsequent pregnancy.
Abstract: OBJECTIVE: To assess the performance of the double marker test [free beta-human chorionic gonadotrophin (beta-hCG) and alpha-fetoprotein (AFP)] as a screening test for Down syndrome in pregnant patients who had a prior renal transplant. DESIGN: A retrospective study. SETTING: The Fetal Medicine Unit, Royal Free Hospital, London, UK. METHODS: Detailed records of 14 post-renal transplant pregnancies were obtained from the Renal Unit of our hospital where the patients were followed up. The serum concentrations of urea, creatinine, free beta-hCG and AFP at the time of the double marker test were recorded, with a cut-off point of 1:250 for the double marker test. A control group of 14 normal pregnancies matched for age, parity and gestational age was used. The Mann-Whitney U-test and t-tests of unequal variance were applied to compare parameters of the study and the control groups. RESULTS: Two patients in each group were high risk for Down syndrome and amniocentesis revealed normal karyotype. No babies with Down syndrome were delivered in either group. Regression analysis showed significant correlation between free beta-hCG and urea concentrations (p<0.001) and free beta-hCG and creatinine concentrations (p<0.001), but not for AFP. CONCLUSIONS: The present study demonstrates that residual renal function alterations persisting after renal transplantation can affect the levels of free beta-hCG and AFP, thus resulting in false-positive screening for Down syndrome. First trimester nuchal translucency (NT) measurement in combination with second trimester ultrasonographic markers can be used in these patients, or alternatively the free beta-hCG levels should be corrected according to the serum creatinine levels.
Abstract: BACKGROUND: Many maternal serum markers show concentration changes in Down's syndrome pregnancies but the magnitude of the change in median marker levels varies with gestation. To date these changes have not been accurately specified. METHODS: The trends in marker median levels between 6 and 20 weeks of gestation were examined for alphafetoprotein (AFP), free beta human chorionic gonadotrophin (Fbeta-hCG), total human chorionic gonadotrophin (ThCG) and pregnancy-associated plasma protein A (PAPP-A) by a meta-analysis of data obtained from our collaborative studies and routine screening programmes for Down's syndrome over a 10-year period. Data were available from between 709 and 1082 Down's syndrome pregnancies and from between 14607 and 153909 unaffected pregnancies for each marker. The median multiple of the median (MoM) and mean log10MoM for each marker at each completed week of gestation were estimated and the trend with gestation smoothed using a weighted least squares regression model. RESULTS: The gestational ages at which maximum separation of marker levels occurred, comparing affected and unaffected pregnancies, and the respective regressed median MoMs and mean log10MoMs, were: for AFP at 16 weeks, 0.72 MoM, -0.14288log10MoM; for Fbeta-hCG at 15 weeks, 2-24MoM, 0.35034 log10MoM; for ThCG at 16 weeks, 1.93 MoM, 0.28548 log10MoM, as well as before 8 weeks (<0.65 MoM, -0.18853 log10MoM); and for PAPP-A before 8 weeks, <0.33 MoM, -0.47727 log10MoM. CONCLUSION: There is significant temporal variation in mean log10MoM values for the screening markers investigated. Screening algorithms, modified to take account of this variation, should allow more accurate gestation-specific risks to be calculated in individual pregnancies.
Abstract: This study examines 45 cases of trisomy 13 and 59 cases of trisomy 18 and reports an algorithm to identify pregnancies with a fetus affected by trisomy 13 or 18 by a combination of maternal age fetal nuchal translucency (NT) thickness, and maternal serum free beta-hCG and PAPP-A at 11-14 weeks of gestation. In this mixed trisomy group the median MoM NT was increased at 2.819, whilst the median MoMs for free beta-hCG and PAPP-A were reduced at 0.375 and 0.201 respectively. We predict that with the use of the combined trisomy 13 and 18 algorithm and a risk cut-off of 1 in 150 will for a 0.3% false positive rate allow 95% of these chromosomal defects to be identified at 11-14 weeks. Such algorithms will enhance existing first trimester screening algorithms for trisomy 21.
Abstract: AIM: To assess whether the uptake of prenatal screening for trisomy 21 in a subsequent pregnancy is influenced by being classified in the 'increased risk' or 'not at increased risk' group in the first pregnancy. SETTING: District General Hospital Maternity Unit. METHODS: Amongst a group of women attending for maternity care at this hospital, the maternity records were examined to find women having at least two pregnancies. Any prenatal screening record for each pregnancy was retrieved from the prenatal screening database. Prenatal screening for trisomy 21 was by a combination of maternal serum alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (beta-hCG) in the second trimester and by maternal serum free beta-hCG and pregnancy-associated plasma protein-A (PAPP-A) and fetal nuchal translucency (NT) thickness in the first trimester. Women were stratified according to their trisomy 21 risk into an 'increased risk' group (1: <250 in the second trimester and 1: <300 in the first trimester) or 'not at increased risk' group based on their first pregnancy. In a second pregnancy, the records were examined to see if the mother accepted prenatal screening in the second pregnancy. The rate of acceptance of screening in a subsequent pregnancy, depending on whether 'at increased risk' or 'not at increased risk' in the first pregnancy, was examined using chi square tests. RESULTS: In the second trimester study, 4601 women were identified with two pregnancies during the study period. Of these, 4559 women had prenatal screening in a subsequent pregnancy. Initially, 273 women were identified in the high-risk group, and of these 252 (92.3%) elected to have prenatal screening in a subsequent pregnancy. This compared with 4307 of 4328 (99.5%) women in the low-risk group. In the first trimester study, 1077 women were identified with two pregnancies during the study period. Of these, 1072 had prenatal screening in a subsequent pregnancy. Initially, 60 women were identified in the high-risk group, and of these 56 (93.3%) elected to have prenatal screening in a subsequent pregnancy. This compared with 1016 of 1017 (99.9%) in the low-risk group. Statistically, there was no difference between the rate of declining prenatal screening in a second pregnancy amongst those in the high-risk group in a first pregnancy or those in the low-risk group (p = 0.429 for second trimester screening and p = 0.794 for first trimester screening). Similarly, no difference could be demonstrated between rates when screening in the first or second trimester (p = 0.961) for those in the high-risk group. CONCLUSION: Despite the understandable anxiety associated with being identified in the high-risk group (as a false positive finding) in a previous pregnancy, this did not seem to deter women from accepting prenatal screening in a subsequent pregnancy.
Abstract: OBJECTIVE: To assess the within person biological variability of first trimester maternal serum biochemical markers of trisomy 21 across the 10-14 week gestational period. To evaluate whether repeat sampling and testing of free beta-hCG and PAPP-A during this period would result in an improved detection rate. METHODS: Women presenting at the first trimester OSCAR clinic have blood collected prior to ultrasound dating and nuchal translucency measurement. All samples are analysed for free beta-hCG and PAPP-A before an accurate estimate of gestation is available. In 10% of cases the gestation is prior to the minimum time for NT measurement (11 weeks) and these women are rebooked for a repeat visit to the clinic at the appropriate time. Our fetal database was interrogated to obtain cases in which two maternal blood samples had been collected and analysed in the 10-14 week period. Using data from the marker correlations and statistical modelling, the impact of repeat testing on detection rate for trisomy 21 at a fixed 5% false positive rate, was assessed. RESULTS: 261 pairs of data were available for analysis collected over a 3 year period. The correlation between free beta-hCG in sample 1 and sample 2 was 0.890 and that for PAPP-A was 0.827. The average within person biological variation for free beta-hCG was 21% and 32% for PAPP-A. The increase in detection rate when using both sets of marker data was 3.5% when using serum biochemistry and maternal age, and 1.3% when using nuchal translucency, serum biochemistry and maternal age. CONCLUSION: Repeat sampling and testing of maternal serum biochemical markers is unlikely to substantially improve first trimester screening performance.
Abstract: In a study of 180 twin pregnancies I have examined the distribution of maternal serum free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A), in addition to fetal nuchal translucency thickness (NT), in twins classified as monochorionic or dichorionic, based on ultrasound appearance at 10-14 weeks of gestation. In 45 monochorionic and 135 dichorionic twin pregnancies the median MoM free beta-hCG was not significantly different (1.00 vs 1.01), whilst that for PAPP-A was lower (0.89 vs 1.01) but again with no statistical significance. Previous reports of an increased fetal NT in monochorionic twins pregnancies could not be confirmed (1.03 vs 1.00). It is concluded that the existing pseudo risk twin correction algorithm is appropriate for both monochorionic and dichorionic twins in providing accurate first trimester risks for trisomy 21.
Abstract: Placenta growth factor (PIGF), an angiogenic factor belonging to the vascular endothelial growth factor family, pregnancy-associated plasma protein A (PAPP-A) and free beta-human chorionic gonadotrophin (beta-hCG) were measured in maternal serum from 45 pregnancies with trisomy 21, 45 with trisomy 18 and 493 normal controls at 10-13 completed weeks of gestation. In the normal pregnancies maternal serum PIGF levels increased exponentially with gestation. The median multiple of the median (MoM) PIGF concentration in the trisomy 21 group (1.26 MoM) was significantly higher (p<0.0001) than in the control group (1.00 MoM). In the trisomy 18 group the median PIGF was lower (0.889 MoM) but this did not quite reach significance (p=0.064). The corresponding median MoM values for PAPP-A were 1.00 MoM for the controls, 0.49 MoM for trisomy 21 and 0.16 MoM for trisomy 18. The median MoM values for free beta-hCG were 1.00 MoM for the controls, 2.05 MoM for trisomy 21 and 0.38 MoM for trisomy 18. In the control group there was a small but significant correlation of PIGF with free beta-hCG (r=+0.1024) and PAPP-A (r=+0.2288). In the trisomy 18 group there was a significant association between PIGF and free beta-hCG (r=+0.2629) but not with PAPP-A (r=+0.0038). In the trisomy 21 group there was a small but significant association with PAPP-A (r=+0.1028) but not with free beta-hCG (r=+0.0339). The separation of affected and unaffected pregnancies in maternal serum PIGF is small, and therefore it is unlikely that measurement of PIGF would improve screening for these abnormalities provided by the combination of fetal nuchal translucency and maternal serum PAPP-A and free beta-hCG.
Abstract: In 45 cases of trisomy 18 and 493 control pregnancies at 10-14 weeks of gestation, maternal serum inhibin A, total activin A, free beta-hCG and PAPP-A were measured. In the trisomy 18 pregnancies the median values were 0.74 MoM for inhibin A, 1.23 MoM for activin A, 0.38 MoM for free beta-hCG and 0.16 MoM for PAPP-A. The degree of deviation from normal in the levels of inhibin and activin is small in comparison with free beta-hCG and PAPP-A and they are therefore unlikely to be of value in improving the sensitivity of 90% for a 1% false-positive rate achieved by screening with fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A.
Abstract: OBJECTIVE: To determine how first trimester detection rates for Down's Syndrome vary with maternal age and to calculate the predictive value of an increased risk report at various maternal ages. DESIGN: Mathematical modelling of first trimester screening performance using fetal nuchal translucency and maternal serum free betahCG and pregnancy associated plasma protein-A (PAPP-A). METHODS: From within the Gaussian distributions of each marker in normal pregnancies and those affected by Down's Syndrome a series of 15,000 marker multiple of the medians were obtained for each group. These markers were then used to calculate the risks of Down's Syndrome using maternal ages ranging from 15 to 49 and the background risk of Down's Syndrome at each age. Using a 1 in 300 risk cutoff (at time of sampling) the false positive rate and detection rate was assessed at each year of maternal age. The predictive value of a positive result was calculated using Baye's theorem. OUTCOME MEASURES: False positive rates and detection rates at each year of maternal age between 15 and 49; the predictive value of a positive result for each maternal age between 15 and 49. RESULTS: At 15 years of age the detection rate was 77% at a 1.9% false positive rate, 84% at a 4% false positive rate at age 30, rising to 100% at a 67% false positive rate at age 49. The probability of Down's Syndrome once identified with an increased risk was 1:34 at 15 years, 1:29 at 30 years and 1:6 at 49 years. CONCLUSIONS: As with second trimester biochemical screening, the detection rate and false positive rate vary considerably with age. However, detection rates across all ages are significantly higher than with second trimester screening. The risk of a positive screening result being a Down's pregnancy is considerably greater than with second trimester screening with an average probability of 1:29, compared with 1:55 in the second trimester. This information may be useful in counselling women with an increased risk result in first trimester screening.
Abstract: In a group of 149 women who had undergone routine first trimester screening using fetal nuchal translucency thickness (NT) and maternal serum free beta-hCG and pregnancy associated plasma protein-A (PAPP-A) in two consecutive pregnancies the within person between pregnancy biological variability of these markers has been assessed. For fetal NT there was no correlation between NT MoM in the first and second pregnancy (r=0.0800). For maternal serum free beta-hCG MoM a significant correlation was observed (r=0.4174) as was also found for PAPP-A MoM (r=0.3270). The implications for such between pregnancy marker association is that women who have an increased risk of Down syndrome in their first pregnancy are 1.5-2 times more likely to repeat this event in their next pregnancy. This observation may be useful in counselling women in the first trimester screening of a subsequent pregnancy.
Abstract: OBJECTIVE: To assess the effectiveness of antenatal screening for trisomy 21 by first trimester sonography followed by second trimester biochemical screening. DESIGN: Retrospective five-year review. SETTING: Maternity unit of a university hospital. POPULATION: An unselected group of 7447 pregnant women who had a first trimester scan and nuchal translucency measurement in our unit after January 1995 and had an estimated date of delivery before 1 January 2000. 11.9% were > or = 37 years old. A subgroup (n = 4,864) also had second trimester biochemical testing by alpha-fetoprotein and free beta-human chorionic gonadotrophin. MAIN OUTCOME MEASURES: Prenatal and postnatal diagnosis of trisomy 21. Results There were 23 fetuses affected with trisomy 21. The overall prenatal detection rate was 87% (20/23; 95% CI 66% to 97%) and we performed invasive procedures in 8.5% of our population. First trimester sonography identified 74% (95% CI 51.6% to 89.8%) of affected fetuses. Second trimester biochemical screening detected half of the fetuses with trisomy 21 which were missed by first trimester screening, increasing the sensitivity to 90.5% (19/21; 95% CI 69.6% to 98.8%) for an invasive procedure rate of 4.2% performed in screened positive women. However, the positive predictive value of the biochemical test was very low (0.5%). In screen negative women, karyotyping for advanced maternal age did not detect any affected fetuses. CONCLUSION: First trimester nuchal translucency measurement is an effective screening test for the prenatal detection of fetuses with Down's Syndrome. Although the measurement of biochemical markers in the second trimester can detect additional affected fetuses this may be outweighed by the delay in diagnosis, the extra visits and cost so that the right time for biochemical screening is most likely to be in the first trimester.
Abstract: OBJECTIVE: To determine whether the reported decrease in maternal serum placenta growth factor concentration in preeclampsia is evident from the first trimester and before clinical onset of the disease. We also examined levels in pregnancies that subsequently resulted in fetal growth restriction (FGR). METHODS: Placenta growth factor concentration was measured in stored maternal serum samples obtained at 11-14 weeks of gestation from 131 women who subsequently developed preeclampsia, 137 women who subsequently developed FGR, and 400 randomly selected controls who did not develop preeclampsia or FGR. Preeclampsia was defined as diastolic blood pressure of 90 mmHg or more on two occasions 4 hours apart, accompanied by proteinuria (more than 300 mg of total protein in a 24-hour urine collection or a positive test for albumin on reagent strip) in women with no pre-existing hypertensive or renal disease. Fetal growth restriction was considered present if a woman subsequently delivered a live infant with a birth weight below the fifth centile for gestation. RESULTS: In the control group, maternal serum placenta growth factor concentration increased with gestation. Compared with the controls (median multiple of the median 0.98, standard deviation [SD] 0.51), levels in the preeclampsia group (median multiple of the median 1.09, SD 0.52) were not significantly different (t = 1.83, P = .07), but in the FGR group (median multiple of the median 1.57, SD 0.74), levels were significantly increased (t = 10.85, P < .001). CONCLUSION: The previously reported decrease in serum placenta growth factor levels in women with preeclampsia might not precede clinical onset of the disease and is not apparent in the first trimester of pregnancy. Levels are significantly increased in pregnancies resulting in FGR.
Abstract: Dimeric inhibin A was measured in maternal serum samples from 45 pregnancies affected by trisomy 21 and 493 samples from unaffected pregnancies at 10-14 weeks of gestation. Inhibin A levels in affected pregnancies were compared with levels of free beta-hCG and PAPP-A in the same series. In the trisomy 21 group, the median multiple of the median (MoM) inhibin A was not significantly elevated (1.28 vs 1.00) with only 15.5% being above the 95th centile. In contrast, the median MoM free beta-hCG was significantly increased (2.05 vs 1.00) with 36% above the 95th centile and PAPP-A was significantly reduced (0.49 vs 1.00) with 42% below the 5th centile. Inhibin A levels in the trisomy 21 group were significantly correlated with gestational age such that median levels rose from 1.04 at 11 weeks to 1.30 at 12 weeks and 1.67 at 13 weeks. These findings suggest that first trimester biochemical screening for trisomy 21, which is currently optimised using maternal serum free beta-hCG and PAPP-A and fetal nuchal translucency, will not benefit from the inclusion of inhibin A.
Abstract: BACKGROUND: The possible effect of assisted reproduction on first-trimester screening for trisomy 21 was examined by fetal nuchal translucency thickness (NT), maternal serum free beta-human chorionic gonadotrophin (HCG) and pregnancy-associated plasma protein-A (PAPP-A). METHODS: Parameters were measured at 11-14 weeks in 411 singleton pregnancies achieved by controlled ovarian stimulation, including 220 that had undergone IVF. Results were compared with 1233 singleton pregnancies conceived spontaneously. RESULTS: In the IVF pregnancies, the median fetal NT was not significantly different from that in controls, whilst the median free beta-HCG was significantly increased, and PAPP-A was significantly decreased. In the intracytoplasmic sperm injection group, fetal NT and free beta-HCG values were not significantly different from those in controls, but PAPP-A was significantly decreased. In those pregnancies achieved by ovarian stimulation, neither fetal NT, free beta-HCG nor PAPP-A were significantly different from the control group. CONCLUSIONS: In IVF pregnancies, screening for trisomy 21 by fetal NT, maternal serum free beta-HCG and PAPP-A levels may be associated with a 1.2% higher false-positive rate than in natural conception.
Abstract: Maternal serum total activin-A concentration was measured in 45 pregnancies affected by trisomy 21 and 493 control unaffected pregnancies at 10-14 weeks of gestation. In the trisomy 21 pregnancies total activin-A concentration was significantly higher (1.36 MoM of the unaffected pregnancies) and in 16% of cases the level was above the 95th centile of normal. The log10 SD for the control group and the trisomy 21 group were 0.17 and 0.22, respectively. The median pregnancy associated plasma protein-A (PAPP-A) in this trisomy 21 series was 0.49 and for free beta-hCG was 2.05. In the trisomy group there were significant positive associations between total activin-A and PAPP-A (0.6071) and free beta-hCG (0.4255). The low median difference and the high overlap in values between trisomic and unaffected pregnancies make total activin-A of little practical use in first-trimester screening for trisomy 21.
Abstract: In 25 cases of triploidy at 10-14 weeks of gestation, compared with 947 controls, the median multiple of the median (MoM) fetal nuchal translucency (NT) thickness was significantly increased (1.89 MoM), and maternal serum total and free beta-human chorionic gonadotrophin (hCG) were increased (3.13 MoM and 4.59 MoM respectively), alpha fetoprotein (AFP) was increased (2.14 MoM), and pregnancy associated plasma protein A (PAPP-A) was decreased (0.12 MoM). There are two types of triploidy. In type I, where the additional chromosome set is of paternal origin, the placenta is partially molar and the fetus is relatively well-grown. Type II, where the extra chromosome set is of maternal origin, is characterized by a small normal looking placenta and severe asymmetrical fetal growth restriction. In type I triploidy there was increased fetal NT (2.76 MoM), maternal serum total hCG (4.91 MoM), free beta-hCG (8.04 MoM), and AFP (3.22 MoM), and mildly decreased PAPP-A (0.75 MoM). In type II triploidy fetal NT was not increased (0.88 MoM), and there was a decrease in maternal serum total hCG (0.16 MoM), free beta-hCG (0.18 MoM), PAPP-A (0.06 MoM) and AFP (0.77 MoM). We conclude that a large proportion of triploidy cases of both phenotypes could be identified in the first trimester using NT, maternal serum free beta-hCG and PAPP-A with a combination of trisomy 21 risk and an atypicality approach.
Abstract: Total human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP) were measured in maternal serum at 10-14 weeks of gestation from 53 pregnancies affected by trisomy 18, 42 cases with trisomy 13, 46 with Turner's syndrome and 13 with other sex aneuploides. The only significant association was the finding of reduced levels of total hCG in cases of trisomy 18 and 13. The association of increased levels of AFP in cases of trisomy 18 with ventral wall defects and the slight increase in AFP in cases of sex chromosomal anomalies other than Turner's syndrome was found. AFP and total hCG are not likely to replace the markers free beta-hCG and PAPP-A in first trimester screening for chromosomal anomalies.
Abstract: In a study of 30 802 unaffected pregnancies and 90 cases of Down syndrome I have analysed second trimester maternal serum alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (beta-hCG) and grouped the data by fetal sex. In pregnancies with an unaffected female fetus maternal serum AFP was significantly lower (3%) than in the presence of a male fetus, whilst free beta-hCG was significantly raised (7%) in the presence of a female fetus. These differences led to a significantly higher false positive rate in women carrying a female fetus (5.78% versus 4.64%). In pregnancies affected by Down syndrome the median AFP in the presence of a female fetus was not significantly different to that with a male fetus (0. 72 versus 0.73); similarly for free beta-hCG the difference (2.37 versus 2.48) was not statistically significant. Although the detection rate amongst male fetuses was slightly higher than in females (74% versus 66%), this was not statistically significant. Although fetal gender does appear to have a significant effect on maternal serum marker levels, leading to a higher false positive rate in females, in cases of Down syndrome there is no evidence that such marker differences are significant and consequently little evidence for any fetal gender bias in detection rates.
Abstract: In a first trimester study of 5422 Caucasian women, 752 Afro-Caribbean women and 170 Asian women we have shown that the median maternal serum marker MoMs for free beta-hCG and PAPP-A were 19% and 48% higher in Afro-Caribbean women and 19% higher and 35% higher in Asian women, compared to Caucasian women. Correcting for maternal weight made very little difference to the effect in Afro-Caribbeans (21% and 57% higher after weight correction) but reduced the effect in Asians (4% and 17% higher after weight correction ). It is estimated that correcting for maternal weight and ethnicity overall would increase the detection rate by a modest 1.4%. However, the effect on an individual's risk could result in as much as a two-fold increase in the patient specific risk for trisomy 21. The impact of ethnic origin seems to be greater than that observed with second trimester biochemical markers and larger studies are required in order to develop robust algorithms for correcting for ethnic origin in the first trimester.
Abstract: We have studied maternal serum free beta-hCG and PAPP-A, and fetal nuchal translucency (NT) in a series of 46 cases of fetal Turner's syndrome, 13 cases of other sex chromosomal anomalies and compared these with 947 control pregnancies in the first trimester. In cases of Turner's syndrome (45,X) the median fetal NT was significantly higher than in controls (4.76 MoM), the median PAPP-A was significantly lower (0.49 MoM), whilst the free beta-hCG was not significantly different (1.11 MoM). For NT, 93% (43/46) of cases were equal to or greater than the 95th centile of controls, for PAPP-A 35% (16/46) of cases were less than or equal to the 5th centile of controls and for free beta-hCG 15% (7/46) of cases were equal to or greater than the 95th centile of controls. For other sex chromosomal anomalies (47XXX, XXY, XYY) the median NT was increased (2.07 MoM) whilst PAPP-A was not significantly decreased (0.88 MoM) and free beta-hCG was not significantly different (1.07 MoM) from controls. Using a previously derived multivariate risk algorithm for trisomy 21, incorporating NT, PAPP-A, free beta-hCG and maternal age, 96% of the Turner's cases and 62% of the other sex chromosomal anomalies would have been identified.
Abstract: In a study of 130 first trimester cases of trisomy 21 and 959 controls we have shown that the median MoM for alpha-fetoprotein (AFP) is lower (0.82) and that for total human chorionic gonadotrophin (hCG) is higher (1.31) than in the control group. For AFP 15.3% of cases were below the 5th centile and for total hCG 19. 8% were above the 95th centile. The median shift observed for AFP and total hCG is poorer than that for pregnancy associated plasma protein-A (PAPP-A) or free beta-hCG and together with maternal age, AFP and total hCG could only be expected to detect 40% of cases. In combination with PAPP-A, total hCG would identify 52% of cases, somewhat less than the 67% observed with free beta-hCG and PAPP-A. However, we have demonstrated for total hCG a significant temporal change in median MoM with gestational age. Before 70 days the median MoM was less than 0.5, between 70 and 83 days this increased to 1.13, and between 84 and 97 days this increased to 1.52. This median shift has significant implications for interpreting previous studies and even more significant implications for detection rates. When population parameters specific to the gestational age in question are used, detection rates with total hCG and PAPP-A increase from 47% at 70-83 days to 60% at 84-97 days. This observation explains much of the confusion around total hCG in the first trimester and shows the importance of selecting analyte pairs and population parameters appropriate to the time in gestation when screening is performed.
Abstract: OBJECTIVES: To determine the effects of chromosomal defects on fetal heart rate at 10-14 weeks of gestation. METHODS: Fetal heart rate at 10-14 weeks of gestation in 1061 chromosomally abnormal fetuses was compared to that from 25,000 normal pregnancies. The chromosomally abnormal group included 554 cases of trisomy 21, 219 cases of trisomy 18, 95 of trisomy 13, 50 of triploidy, 115 of Turner syndrome and 28 of sex chromosome abnormalities other than Turner syndrome. RESULTS: In the normal group, fetal heart rate decreased from a mean value of 170 beats per minute (bpm) at 35 mm of crown-rump length to 155 bpm at 84 mm crown-rump length. In trisomy 21, trisomy 13 and Turner syndrome fetal heart rate was significantly higher, in trisomy 18 and triploidy the heart rate was lower and in other sex chromosome defects it was not significantly different from normal. Fetal heart rate was above the 95th centile of the normal range in 10%, 67% and 52% of fetuses with trisomy 21, trisomy 13 and Turner syndrome, respectively. The fetal heart rate was below the 5th centile in 30% of fetuses with triploidy and 19% of those with trisomy 18. CONCLUSIONS: Trisomy 21, trisomy 13 and Turner syndrome are associated with fetal tachycardia, whereas in trisomy 18 and triploidy there is fetal bradycardia. Inclusion of fetal heart rate in a first-trimester screening program for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness is unlikely to provide useful improvement in sensitivity.
Abstract: In 42 cases of trisomy 13 at 10-14 weeks of gestation, compared with 947 controls, the median multiple of the median (MoM) of maternal serum free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy associated plasma protein A (PAPP-A) was significantly decreased (0.506 MoM and 0.248 MoM respectively), whilst fetal nuchal translucency was increased (2.872 MoM). In 38% and 71% of cases of trisomy 13 maternal serum free beta-hCG and PAPP-A was below the 5th centile of the appropriate normal range for gestation and in 62% of cases the nuchal translucency was above the 95th centile. When combined together in a multivariate algorithm with maternal age, 90% of cases of trisomy 13 could be detected at a 0.5% false positive rate or 84% at a 0.1% false positive rate. We conclude that specific trisomy 13 risks should be part of developing risk algorithms combining maternal serum biochemistry and nuchal translucency for use in first trimester screening alongside those for trisomy 21 and trisomy 18.
Abstract: In a study of 2923 normal pregnancies and 203 pregnancies affected by trisomy 21 we have shown a significant difference in the median MoM of the markers: fetal nuchal translucency, maternal serum free beta-hCG and PAPP-A in the presence of a female fetus compared with a male fetus. For maternal serum free beta-hCG levels are higher by 15% if the fetus is chromosomally normal and by 11% if the fetus has trisomy 21. For maternal serum PAPP-A the levels in chromosomally normal fetuses are 10% higher in the presence of a female fetus and 13% higher if the fetus has trisomy 21. In contrast, fetal nuchal translucency is 3-4% lower in both chromosomally normal and trisomy 21 female fetuses. The consequence of such changes when screening for trisomy 21 will be a reduction in the detection rate in female fetuses by a factor of 1-2%. Correction of risk algorithms for fetal sex, however, is probably not feasible, since ultrasound detection of fetal sex is only 70-90% accurate in the 10-14 week period.
Abstract: OBJECTIVE: To evaluate the introduction of a one stop multidisciplinary clinic for screening for fetal chromosomal abnormalities in the first trimester by a combination of maternal serum biochemistry and ultrasonography providing a risk of chromosomal abnormalities within a one hour clinic visit. DESIGN: One year retrospective review of screening performance. POPULATION: All women attending for routine antenatal care. The population included 4,190 singleton pregnancies in women of all ages screened between 10 weeks and 3 days and 13 weeks and 6 days of gestation between the periods 1 June 1998 and 31 May 1999 in a district general hospital antenatal clinic. METHODS: All women booked into the clinic were offered screening by a combination of maternal serum free beta human chorionic gonadotrophin (hCG) and pregnancy associated plasma protein A (PAPP-A) and fetal nuchal translucency thickness. Women at increased risk of carrying a fetus with trisomy 21 or trisomy 18/13 (> or =1 in 300 at sampling) were offered counselling and an invasive diagnostic procedure. Follow up of the outcome of all pregnancies was carried out. MAIN OUTCOME MEASURES: The detection rate for trisomy 21, trisomy 18/13 and all aneuploides, false positive rate, uptake of screening, uptake of chorionic villus sampling in women identified at increased risk and fetal loss after chorionic villus sampling. RESULTS: Overall 97.6% of the women (4,088/4,190) accepted first trimester screening. The rate of detection of trisomy 21 was 86% (6/7), for trisomy 18/13 100% (9/9) and for all aneuploides 95% (18/19). Fetal death at presentation was found in 1.6% of pregnancies (69/4,088). Of women who accepted screening, 6.1% (257/4,088) presented too late for fetal nuchal translucency measurement and 6.5% of the women (271/4,088) presented too early. The false positive rate was 6.7% (253/3,762). Uptake of invasive testing was 83% (207/253). CONCLUSION: First trimester prenatal screening for chromosomal abnormalities using a combination of maternal serum biochemistry and fetal nuchal translucency thickness can achieve detection rates in excess of 90%. These services can be provided in a one stop multidisciplinary clinic.
Abstract: We have studied changes in first trimester fetal nuchal translucency (NT) and maternal serum free beta-hCG and PAPP-A with gravidity and parity in 3252 singleton pregnancies unaffected by chromosomal abnormality or major pregnancy complications. We have shown that gravidity and parity is associated with a small but progressive decrease in fetal NT and a small but progressive increase in free beta-hCG and PAPP-A. None of these small changes with increasing gravidity or parity are statistically significant and hence correction for these variables is not necessary when considering first trimester screening for chromosomal abnormalities.
Abstract: OBJECTIVE: To examine the value of first trimester maternal serum free beta human chorionic gonadotrophin (beta hCG) and pregnancy associated plasma protein A (PAPP-A) as predictors of pregnancy complications. DESIGN: Screening study. SETTING: Antenatal clinics. POPULATION: Singleton pregnancies at 10-14 weeks of gestation. METHODS: Maternal serum free beta hCG and PAPP-A were measured at 10-14 weeks of gestation in 5,584 singleton pregnancies. In the 5,297 (94.9%) pregnancies with complete follow up free beta hCG and PAPP-A were compared between those with normal outcome and those resulting in miscarriage, spontaneous preterm delivery, pregnancy induced hypertension or fetal growth restriction and in those with pre-existing or gestational diabetes. RESULTS: Maternal serum PAPP-A increased and beta hCG decreased with gestation. The multiple of median maternal serum PAPP-A was significantly lower in those pregnancies resulting in miscarriage, pregnancy induced hypertension, growth restriction and in those with pre-existing or gestational diabetes mellitus, but not in those complicated by spontaneous preterm delivery. The level was < 10th centile of the reference range in about 20% of the pregnancies that subsequently resulted in miscarriage or developed pregnancy induced hypertension or growth restriction, and in 27% of those that developed gestational diabetes. Maternal serum free beta hCG was < 10th centile of the reference range in about 15% of the pregnancies that subsequently resulted in miscarriage or developed pregnancy induced hypertension or growth restriction, and in 20% of those that developed gestational diabetes. CONCLUSION: Low maternal serum PAPP-A or beta hCG at 10-14 weeks of gestation are associated with subsequent development of pregnancy complications.
Abstract: In the first trimester of pregnancy the biochemical markers free beta-hCG and pregnancy associated plasma protein-A (PAPP-A) are used for the prenatal screening of trisomy 21, either alone or in combination with nuchal translucency (NT) thickness. In this study, I have analysed the distribution of these biochemical markers in 159 twin pregnancies and compared this with 3466 singleton pregnancies. On average free beta-hCG values are 2.099 times greater in twins than in singletons and PAPP-A some 1.86 times greater. The width of the analyte distribution in twins is very similar to that in singleton pregnancies. Using statistical modelling techniques I have predicted that at a 5% false positive rate the detection rate in twins discordant for trisomy 21 will be 52% and in twins concordant for trisomy 21 will be 55%, if correction for twin pregnancy is carried out using the 'pseudo risk' approach. The detection rate using biochemical parameters is less than that achievable for twins using NT (75%). However, the combination of NT and maternal serum biochemistry will give detection rates approaching 80%. These rates are some 10% less than in singleton pregnancies, but nevertheless combining NT and biochemistry will allow high rates of detection of affected twins with the benefit of ultrasound and NT being able to specifically locate the affected twin. Twin screening using both modalities should be considered when introducing first trimester screening.
Abstract: In a group of 26 524 control pregnancies and a group of 3728 pregnancies affected by one or more of the pregnancy complications of low birthweight, intra-uterine growth restriction (IUGR), preterm delivery and stillbirth, I have compared the relative risk of occurrence of these complications in pregnancies which had a raised maternal serum AFP (>2.0 MoM), raised maternal serum free beta-hCG (>2.0 MoM), low AFP (<0.5 MoM), low free beta-hCG (<0.5 MoM), combined raised AFP and free beta-hCG (>2.0 MoM), and in those with an increased Down syndrome risk (1 in 250 or greater). In the low birthweight group, only an increased AFP and decreased free beta-hCG showed significance with relative risks of 1.6 and 2.1. In the IUGR group, also only an increased AFP and decreased free beta-hCG showed significance with relative risks of 1.6 and 2.3. In the preterm delivery group, raised AFP, reduced free beta-hCG, and combined elevated AFP and free beta-hCG showed significance with relative risks of 3.8, 1.8 and 6.2. In the stillbirth group, raised AFP, reduced free beta-hCG, and combined elevated AFP and free beta-hCG showed significance with relative risks of 4.5, 2,4 and 7.2. An isolated raised free beta-hCG or an increased Down syndrome risk were not associated with an increased relative risk for any of the pregnancy complications investigated. However, apart from the six to seven-fold increased risk when both AFP and free beta-hCG are above 2.0 MoM, suggesting increased risk of preterm delivery or impending fetal death, the clinical utility of such significant differences is probably poor.
Abstract: OBJECTIVE: To examine the potential impact of combining maternal age with fetal nuchal translucency thickness and maternal serum free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) in screening for trisomy 21 at 10-14 weeks of gestation. METHODS: Maternal serum free beta-hCG and PAPP-A were measured by Kryptor, a random access immunoassay analyzer using time-resolved amplified cryptate emission, in 210 singleton pregnancies with trisomy 21 and 946 chromosomally normal controls, matched for maternal age, gestation and sample storage time. In all cases the fetal crown-rump length and nuchal translucency thickness had been measured by ultrasonography at 10-14 weeks of gestation and maternal blood had been obtained at the time of the scan. The distributions (in multiples of the median; MoM) of free beta-hCG and PAPP-A (corrected for maternal weight) and fetal nuchal translucency (NT) were determined in the trisomy 21 group and the controls. Likelihood ratios for the various marker combinations were calculated and these were used together with the age-related risk for trisomy 21 in the first trimester to calculate the expected detection rate of affected pregnancies, at a fixed false-positive rate, in a population with the maternal age distribution of pregnancies in England and Wales. RESULTS: In a population with the maternal age distribution of pregnancies in England and Wales, it was estimated that, using the combination of maternal age, fetal nuchal translucency thickness and maternal serum free beta-hCG and PAPP-A, the detection of trisomy 21 pregnancies would be 89% at a fixed false-positive rate of 5%. Alternatively, at a fixed detection rate of 70%, the false-positive rate would be 1%. The inclusion of biochemical parameters added an additional 16% to the detection rate obtained using NT and maternal age alone. CONCLUSIONS: Rapid diagnostic technology like Kryptor, which can provide automated reproducible biochemical measurements within 30 min of obtaining a blood sample, will allow the development of interdisciplinary one-stop clinics for early fetal assessment. Such clinics will be able to deliver improved screening sensitivity, rapidly and more efficiently, leading to reduced patient anxiety and stress.
Abstract: The aim of this study was to investigate the second trimester concentrations of maternal urine human chorionic gonadotrophin beta-core fragment (HCGbetacf) in Asian pregnanci2es with fetal chromosomal abnormalities. HCGbetacf concentrations were analysed from 34 urine samples in chromosomally abnormal pregnancies, including 28 cases of Down's syndrome, one case of trisomy 18, and five cases of other chromosomal abnormalities (one mosaic deletion and four translocations), and in a cohort of 268 normal pregnancies receiving second trimester amniocentesis. Results were normalized to urine creatinine (Cr) concentration and converted to the multiple of the median (MOM) concentration for the appropriate gestation. The median HCGbetacf MOM concentrations of Down's syndrome pregnancies (12.89) was significantly higher than that of normal pregnancies (1. 06) (P < 0.00001). Wide variations of HCGbetacf concentrations were observed in other chromosomally abnormal pregnancies. There were 18 of 28 (64%) Down's syndrome cases but one of five (20%) other chromosomally abnormal cases with HCGbetacf concentrations above the 95th centile of the control values (8.22 MOM cut-off). These findings suggest that HCGbetacf could be a potential marker in urine screening for fetal Down's syndrome in Asians.
Abstract: OBJECTIVE: To evaluate second-trimester free beta-hCG and total estriol (E3) in the maternal urine as markers for Down syndrome screening in an Asian population. METHODS: Free beta-hCG and total E3 were measured in the urine samples of 28 Taiwanese Down syndrome pregnancies and 268 unaffected singleton pregnancies at 14-25 weeks. Results were normalized to urine creatinine concentrations and converted to multiples of the median (MoM) levels. Gestational ages were estimated by ultrasound measurements. RESULTS: Median values of free beta-hCG, total E3, free beta-hCG to total E3 ratio, and the free beta-hCG to total E3 MoM ratio in Down syndrome pregnancies were 4.75 MoM, 0.66 MoM, 8.99 MoM, and 9.51, respectively. At a 5% false-positive rate, the observed detection rates were 36% (ten of 28) with total E3, 71% (20 of 28) with free beta-hCG, 68% (19 of 28) with free beta-hCG/total E3, and 71% (20 of 28) with free beta-hCG/total E3 MoM. When combined with maternal age, the expected detection rates were 65% with total E3, 71% with free beta-hCG, 76% with free beta-hCG/total E3, 80% with free beta-hCG/total E3 MoM, and 89% when combining free beta-hCG, total E3, and maternal age. CONCLUSION: Urine free beta-hCG and total E3 are useful markers for Down syndrome screening during the second trimester in Taiwanese women.
Abstract: In a study of 69 random urine samples from cases of Down syndrome and 405 samples from unaffected pregnancies, we have assessed the value of various candidate markers that have been proposed as tools for screening for Down syndrome. We found that the marker urine free beta hCG in Down syndrome had a median MoM of 3.53 (95 per cent confidence interval 2.48-4.68) and at a 5 per cent cut-off would have identified 49 per cent (34/69) of cases. Urine beta core had a median MoM of 4.95 (3.87-8.62) and at a 5 per cent cut-off would have identified 39 per cent (27/69) of cases. Total oestriol had a median MoM of 0.65 (0.55-0.80) and at a 5 per cent cut-off would have identified 35 per cent (24/69) of cases. In conjunction with maternal age, the modelled detection rate increased to 55.8 per cent for free beta hCG, 49.8 per cent for beta core and 48.8 per cent for total oestriol. In combination free beta hCG, total oestriol and maternal age would have detected 68 per cent of cases for a 5 per cent false-positive rate. Using analyte ratios to obviate the need to correct for urine dilution in our study (rather than correcting to a fixed creatinine concentration) was not shown to be as effective as correcting using urine creatinine. Urine markers on the whole are unlikely to be of practical screening value considering the 85 per cent to 90 per cent detection rates achievable in the first trimester using a combination of ultrasound and maternal serum biochemistry.
Abstract: In a study of 50 cases of trisomy 18 compared with 947 controls we have found the median multiple of the median (MoM) of maternal serum free beta human chorionic gonadotrophin to be significantly decreased (0.281 MoM) in samples collected between the 10th and 14th week of gestation. Similarly, maternal serum pregnancy associated plasma protein A (PAPP-A) levels are also decreased (0.177 MoM), whilst the median nuchal translucency is significantly higher (3.272 MoM). Free beta-hCG MoM was less than the 5th centile of normal in 64 per cent of cases of trisomy 18 and for PAPP-A was less than the 5th centile in 78 per cent of cases. Also, in 78 per cent of cases the nuchal translucency was above the 95th centile. When combined together in a multivariate algorithm with maternal age, we predict that 89 per cent of cases of trisomy 18 could be detected at a 1 per cent false-positive rate. We conclude that specific trisomy 18 risks should be part of developing risk algorithms combining maternal serum biochemistry and nuchal translucency for use in first trimester screening alongside those for trisomy 21.
Abstract: Down's syndrome screening in the second trimester using a variety of combinations of maternal serum markers has become an established part of antenatal care over the past decade. The methodology of calculating Down's syndrome risk using statistical models based on the Gaussian distribution functions of the various markers used is often considered daunting, and many screening centres rely on specific screening computer software to undertake the relevant calculations. Such software is often a closed system which does not allow the user to check or change any of the parameters within the model. It is clear from a recent UK NEQAS survey of Down's syndrome screening laboratories (Spencer, Ellis, Seth, 1997, unpublished data) that many centres are unsure what method of calculating risk and what population parameters are used in their software, and how appropriate these are for the population being screened. This confusion has led to uncertainty over the reliability of the risk estimates produced in Down's syndrome screening programs.
Abstract: OBJECTIVE: To determine the value and impact over a seven year period of a second trimester screening programme for trisomy 21 and trisomy 18, using the two maternal serum markers alpha-fetoprotein and free beta human chorionic gonadotrophin. DESIGN: Retrospective review. SETTING: A biochemical screening laboratory serving three health districts with three antenatal clinics in both teaching and nonteaching hospitals. POPULATION: 67,904 pregnancies in women of all ages screened between 14 and 22 weeks of gestation between 1 April 1991 and 31 March 1998. METHODS: All women booked into three major antenatal clinics were offered biochemical screening. Women at increased risk of trisomy 21 or trisomy 18 (> or =1 in 250 at term) were offered an invasive diagnostic procedure. Follow up of the outcome of all pregnancies was performed. MAIN OUTCOME MEASURES: Detection rate for trisomy 21 and trisomy 18, false positive rates, uptake of screening, uptake of amniocentesis in women identified at increased risk, prevalence of trisomy 21 at birth, detection and false positive rates by maternal age, fetal loss rate after amniocentesis, report turn around time, and identification of other anomalies. RESULTS: Overall, 87% (67,904/78,501) of women underwent screening. The rate of detection of trisomy 21 was 75% (80/107; 95% CI 66 to 83) with a 5.1% false positive rate (3466/67,904; CI 4.9 to 5.3%). In women under 30 years of age the detection rate was 60% (18/30; CI 41 to 77) with a 2.6% false positive rate (956/36,371; CI 2.5 to 2.8). The rate of detection of trisomy 18 was 57% (8/14; CI 29 to 82) with a 0.7% false positive rate (475/67,904; CI 0.64 to 0.76). Uptake of amniocentesis was 83% (2912/3508). Women were 3.3 times more likely to refuse amniocentesis if the risk was close to the cutoff (1 in 250) than if the risk was > or =1 in 50. Fetal loss within 28 days of amniocentesis was 0.9% (25/2912). Prenatal screening identified 84 other anomalies in addition to 41 cases of impending fetal death. CONCLUSION: Second trimester prenatal screening for trisomy 21 and trisomy 18 using a simple two marker approach incorporating free beta hCG can achieve high detection rates over a long period of time. Health authorities who still have not introduced trisomy 21 screening should be encouraged by what can be achieved and should consider making such screening available to all women. Established second trimester detection rates of 75% for a 5% false positive rate will be the benchmark by which first trimester screening using nuchal translucency, PAPP-A and free beta hCG will be judged.
Abstract: In an analysis of 3111 singleton pregnancies routinely screened in the first trimester with nuchal translucency, free beta hCG and pregnancy associated plasma protein A (PAPP-A) smoking has been found to occur in 20.8 per cent of pregnant women. When the individual marker levels were assessed in smokers and non-smokers, levels of PAPP-A were reduced in smokers by some 15 per cent. Despite free beta hCG levels being reduced by 10-14 per cent in the second trimester of smoking women, in the first trimester period this is not evident. Simulation studies would suggest that in smokers the detection of trisomy 21 using free beta hCG, PAPP-A and maternal age will be reduced by some 5 to 6 per cent compared with that of the general population.
Abstract: In a study of 70 cases of trisomy 18 and 450 matched controls in the second trimester we have measured the maternal serum levels of the analytes alpha feto protein (AFP), free beta-human chorionic gonadotrophin (hCG) and pregnancy associated plasma protein-A (PAPP-A). We have found the median multiple of the median (MoM) of maternal serum free beta-hCG to be significantly lower (0.327) than normal, as was the level of AFP (0.600). Levels of PAPP-A were reduced even further (0.108). Of the markers associated with trisomy 18 at this time PAPP-A was the most discriminatory, being lower than the 5 per cent centile of normal in 93 per cent of cases, compared with 57 per cent of cases for free beta-hCG and 32 per cent of cases for AFP. Combining free beta-hCG and PAPP-A or all three markers with maternal age would have the ability to detect 74 per cent of cases at a 0.5 per cent false positive rate (or 64 per cent at a 0.1 per cent false positive rate). Unlike in cases of trisomy 21, the low PAPP-A values observed in the first trimester are continued into the second trimester. Whether the good discriminatory power of PAPP-A can be realized in second trimester screening programmes will depend on developing two stage screening algorithms. This approach is unlikely to be better than the excellent detection rates achievable with free beta-hCG, PAPP-A and nuchal translucency in the first trimester.
Abstract: I have studied the impact of maternal smoking on the levels of maternal serum alpha-fetoprotein (AFP) and free beta human chorionic gonadotrophin (hCG) during the second trimester in a large series (30,727) of self-reported smokers and non-smokers whose pregnancy resulted in the birth of a normal fetus. I have confirmed in a smaller subset of this population that self-reporting is an accurate method of assessing smoking status as confirmed by biochemical (serum cotinine) assessment. In addition, I have investigated marker levels among 195 pregnancies affected by Down syndrome with smoking status confirmed by measurement of serum cotinine. In both unaffected and Down syndrome groups, the incidence of smoking was 19 per cent but a considerable variation was observed with maternal age when the incidence in younger women (under 25) was 32 per cent. AFP median levels in unaffected smokers were 3 per cent higher, whilst in the Down syndrome group smoker medians were increased by 10 per cent compared with the non-smoker group. Free beta hCG levels in unaffected smokers were reduced by 14 per cent, whilst in the Down syndrome group smoker median levels were decreased by 16 per cent. In the smoker group, the Down syndrome detection rate was 10 per cent lower than in the non-smoker group, whilst the false-positive rate was also 2 per cent lower. Correcting for smoking status would redress this inequality and produce an overall 2 per cent increase in the detection rate for a 0.4 per cent increase in the false-positive rate. This increase in screening performance may be worth building into screening programmes, particularly in populations with a high smoking incidence.
Abstract: The development of a sensitive and specific enzyme-linked immunoassay (ELISA) for inhibin A stimulated the observation that inhibin A was a useful prenatal marker of Down's syndrome. Modifications of that ELISA, in terms of preassay sample treatment, detection methods and standard preparation, were subsequently introduced to improve assay performance and reduce costs. These modified formats have been validated and reported. We describe the modifications in detail, explaining the rationale for each, and report the results of a study directly comparing the various ELISA formats in terms of assay performance when applied to clinical samples and ability to differentiate between normal and Down's syndrome pregnancies. A format involving sample pretreatment with sodium dodecylsulphate at 100 degrees C was found to give better assay performance and a modest improvement in discrimination between Down's syndrome samples and controls, and we recommend this format for use by other investigators.
Abstract: We have examined maternal urine concentrations of beta core, free beta human chorionic gonadotrophin (hCG), and total oestriol in 373 control pregnancies and 43 pregnancies affected by aneuploidy (including 22 cases of Down's syndrome) in an attempt to see if any of the analytes have a value in Down's syndrome screening between the tenth and 14th week of pregnancy. We have compared the performance of these analytes against nuchal translucency measurement combined with maternal serum free beta hCG at the same period of pregnancy. Our results show that levels of urine free beta hCG and beta core are increased in Down's syndrome with average multiple of the median levels of 1.81 and 2.91, respectively. Urine total oestriol was reduced (0.83) whilst maternal serum free beta hCG was increased (1.72). In trisomy 18 the levels of all analytes were reduced, although serum free beta hCG was the most discriminating. The spread of results in the control and the Down's group for urine beta core was more than three times than that for serum free beta hCG and with urine free beta hCG it was two times wider. In combination with maternal age, urine total oestriol had a 32 per cent detection rate at a fixed 5 per cent false-positive rate; urine beta core 34 per cent, urine free beta hCG 36 per cent, maternal serum free beta hCG 44 per cent, and nuchal translucency 82 per cent. In combination with nuchal translucency, urine total oestriol added an extra 1 per cent detection, urine beta core an extra 2 per cent, urine free beta hCG an extra 3 per cent, and serum free beta hCG an extra 5 per cent. It is unlikely that any of the urine markers will be of value in first-trimester screening. Optimal first-trimester screening programmes will rely for the foreseeable future on nuchal translucency, serum free beta hCG, and possibly pregnancy-associated plasma protein A.
Abstract: In women who have an increased Down syndrome risk in a first pregnancy there is a five-fold greater chance of also having an increased Down syndrome risk in a second subsequent pregnancy. Similarly, in women who have a high alpha-fetoprotein (AFP) level in the first pregnancy, suggesting an increased risk of a neural tube defect (NTD), there is also a five-fold greater chance of them also having a high result in a second subsequent pregnancy. Such a biological association of serum marker levels between pregnancies suggests that there are additional maternal or genetic factors influencing the levels of these serum markers, other than the physiological factors which in themselves are poorly understood. In theory, it is possible to correct for high/low marker results in a previous pregnancy and to do so, I estimate, would reduce the overall Down syndrome screening false-positive rate by about 0.2 per cent. There are insufficient data to make any prediction regarding the impact on detection rates. The small reduction in false-positive rate is unlikely to be a feature worth implementing in Down syndrome screening programmes.
Abstract: In a study of amniotic fluid from 91 Down's syndrome cases and 240 controls, we have shown that the median values of four biochemical markers (AFP, total hCG, free beta hCG, and unconjugated oestriol) in the amniotic fluid of pregnancies affected by Down's syndrome on the whole reflect those observed in the maternal serum of affected cases. The median MOM for AFP was lower than average (0.56), as was that for unconjugated oestriol (0.55), whilst those for total hCG (1.82) and free beta hCG (2.10) were increased on average. The width of the distribution of marker levels in amniotic fluid is similar to that in serum for free beta hCG and total hCG but between 1.5 and 2 times wider for unconjugated oestriol and AFP. Analysis of data by fetal sex showed a significantly higher median MOM in female control cases compared with male controls for the analytes free beta hCG, total hCG, and unconjugated oestriol, but not for AFP. Amongst the Down's syndrome cases, this trend was not statistically significant and we cannot confirm a previous study which reported that elevated levels of amniotic fluid total and free beta hCG were associated only with female fetuses.
Abstract: Maternal serum alpha-fetoprotein concentration was determined in nine pregnancies with fetal anencephaly, seven with exomphalos containing liver, two with spina bifida and 100 normal controls at 10 to 14 weeks of gestation. The median alpha-fetoprotein in the group with fetal anencephaly and exomphalos was significantly higher than in normal fetuses but the sensitivity of this test is likely to be only about 30% for a false positive rate of 5%.
Abstract: We present a case of a monozygotic twin pregnancy who underwent routine screening for chromosomal abnormalities at 14 weeks of gestation by ultrasonographic measurement of nuchal translucency and biochemical analysis of maternal serum alpha fetoprotein and free beta human chorionic gonadotrophin levels. Both screening methods indicated the pregnancy to be at increased risk of Down syndrome, with the ultrasound findings suggesting both fetuses to be affected. An amniocentesis was performed, and karyotype analysis revealed trisomy 21 in both fetuses; the mother subsequently opted for a termination of pregnancy. This case illustrates that screening for trisomy 21 in twin pregnancies is possible by both nuchal translucency measurement and maternal serum markers.
Abstract: OBJECTIVE: Gaussian equation curves are used to generate baseline curves against which a priori maternal age Down syndrome risks are adjusted to develop likelihood ratios for individual patients. We sought to evaluate the accuracy of these calculations, minimize the affects of outliers, and to make improvements. STUDY DESIGN: Gaussian distribution functions were used to investigate the best model for alpha-fetoprotein and free beta-human chorionic gonadotropin multiples of the median with use of nonlinear regressions. Parameters from distribution functions can be used to compute a more precise likelihood ratio for the decision logic for trisomy 21. A total of 58,297 normal cases and 348 cases of trisomy 21 were computed. RESULTS: Log normal distribution functions generated by nonlinear regression produced excellent but exaggerated goodness of fit R2 to the frequency distributions of the data. For normal cases values were as follows (in mean, SD, and R2, respectively): log alpha-fetoprotein -0.07199, 0.15681, and 0.9970; log beta-human chorionic gonadotropin -0.15203, 0.24284, and 0.9987. For trisomy 21 cases the values were (in mean, SD, and R2, respectively) for log alpha-fetoprotein -0.19303, 0.15802, and 0.9828 and for log beta-human chorionic gonadotropin 0.19996, 0.29760, and 0.9669. Distributions reconstructed with use of statistical means and SDs generated goodness of fit R2 from 0.585 to 0.914. Use of means and SDs derived from distribution functions increased the R2 to 0.855 and 0.999. The change in the model produces, at a 5% false-positive rate, a sensitivity of 57.18% (199/348). A 1 in 113 cutoff point risk is obtained and is tighter than the 1 in 251 without the distribution functions, as versus 1 in 270 by age calculations alone. CONCLUSIONS: Our data suggest that (1) normality of log transforms of alpha-fetoprotein and normality of log transforms of beta-human chorionic gonadotropin are reasonable models, (2) distribution functions can minimize the effect of outliers, which produces more realistic risk estimates, and (3) the effect of distribution functions versus standard mean and SDs cannot automatically be extrapolated to other parameters, which must be tested individually.
Abstract: High free beta human chorionic gonadotropin (beta-hCG) and low alpha-fetoprotein (AFP) levels were found in 47 Asian Down's syndrome pregnancies (median values 2.79 and 0.77 MOM, respectively). At a 5 per cent false-positive rate, free beta-hCG alone would identify 46.8 per cent of Down's syndrome pregnancies, age alone detected 34.5 per cent of affected cases, whilst AFP alone detected 17 per cent and free beta-hCG/AFP MOM ratios detected 48.9 per cent of Down's syndrome cases. When combined with maternal age-specific risk, free beta-hCG could achieve a 59.6 per cent detection rate, with AFP achieving 42.6 per cent, free beta-hCG/AFP MOM ratios 61.7 per cent, and combined free beta-hCG and AFP a detection rate of 63.8 per cent for a 5 per cent false-positive rate. Down's syndrome screening at an early gestational age (before 18 weeks) could achieve a 68 per cent detection rate with a 5 per cent false-positive rate, compared with a 59.1 per cent detection rate for a 5.2 per cent false-positive rate when screening at a late gestational age. The use of free beta-hCG in Down's syndrome screening programmes can yield an improved efficacy in the detection of Down's syndrome in an Asian population.
Abstract: In a study of amniotic fluid from 91 Down syndrome cases and 240 controls, we have shown that the median value of CA125 in pregnancies affected by Down syndrome on the whole reflects those observed in the maternal serum from 106 affected cases and 238 controls. The median MOM for CA125 in amniotic fluid from Down syndrome pregnancies was 1.04 and in maternal serum 1.06, neither value being significantly different from that for the control population. We confirm our previous observation that CA125 is not a marker of Down syndrome and conclude that CA125 has no role to play in Down syndrome screening.
Abstract: Serum screening for fetal Down's syndrome in the second trimester is far more efficient in older mothers than in younger ones because the risk calculation is based on maternal age. In recent publications, several authors have tried to better the 'classical' test for Down's syndrome screening by creating an age-independent index. This procedure, however, requires the assumption that at least for one parameter the mean MOM or the variance is not constant in relation to maternal age, leading to a smaller overlap in younger women. This study, based on almost 3000 normal cases and 161 cases with Down's syndrome, could not demonstrate any relationship between maternal age and MOM distribution for alpha-fetoprotein, unconjugated oestriol, total human chorionic gonadotropin (hCG), and free beta hCG. We conclude that for a constant false-positive rate, the detection rate of the 'classical' test for Down's syndrome screening in younger women cannot be bettered by creating an age-independent index.
Abstract: Fourteen cases of Turner syndrome (45,X), two cases of mosaic Turner syndrome (45,X/47,XXX and 45,X/ 46,XX), and one case of Turner syndrome involving an isochromosome X [46,X,i(X)(q10)] were ascertained by prenatal maternal serum alpha-fetoprotein (MSAFP) and free beta human chorionic gonadotropin (hCG) screening or by ultrasound. Patient-specific risks for Down syndrome were calculated and used as the criteria to determine offering further testing. Eleven of the 17 cases had hydrops and presented with an increased Down syndrome risk based on MSAFP and free beta hCG screening. The median MOM level was 0.98 and 4.04 for MSAFP and free beta hCG, respectively. Three cases had hydrops but screened negative. The two cases of mosaic Turner syndrome were non-hydropic and screened positive. The 46,X,i(X)(q10) case was non-hydropic but had elevated MSAFP and free beta hCG levels. These data suggest that Turner syndrome pregnancies do not appear to screen positive due to hydrops alone, but screening may also be influenced by the inherent genetic imbalance in the fetus and placenta. Because the MSAFP levels in our series were within the normative range in all except one case with an elevated MSAFP, free beta hCG alone was the most effective screening marker for Turner syndrome pregnancies.
Abstract: Initial studies of immunoreactive inhibin using a commercial assay have shown levels to be increased in three second-trimester series of maternal samples from Down's syndrome-affected pregnancies. This assay detected non-specifically all forms of circulating inhibin, dimeric and free alpha subunits, whether fully or partially processed. More recently, a new specific assay for dimeric inhibin-A has shown elevated results in both a first-trimester and a second-trimester series of cases. In order to assess the value of dimeric inhibin-A as a potential marker in the second trimester, we have analysed 157 Down's syndrome cases and used 367 unaffected cases across the gestational range 14-20 weeks to establish control medians and population parameters. In our series, the median MOM in Down's cases was 1.77, significantly higher than in the controls. At a 5 per cent false-positive rate, dimeric inhibin-A alone identified 37 per cent of cases. When used in conjunction with maternal age and other marker combinations, mathematical modelling showed detection rates rising from 48 per cent (inhibin-A plus age) to 61 per cent (inhibin-A, free beta hCG, age) and 68 per cent (inhibin-A, AFP, free beta hCG, age). Our data suggest that dimeric inhibin-A may have greater potential earlier in gestation when median levels at 14-16 weeks are 1.92 compared with 1.46 at 17-23 weeks. Dimeric inhibin-A may be a valuable addition to screening protocols, particularly in early gestations.
Abstract: Urine beta core was shown in recent studies to be markedly elevated in pregnancies affected by Down's syndrome in the late second trimester. Free beta human chorionic gonadotropin (hCG) has also been shown to be the most discriminatory maternal serum marker of Down's syndrome. Since free beta hCG is rapidly cleared from the maternal circulation, we have carried out a study to evaluate whether free beta hCG is elevated in the urine of pregnancies affected by Down's syndrome and to investigate whether urine beta core or urine free beta hCG may be used as possible screening markers. Urine samples from 29 cases of Down's syndrome, three cases of trisomy 18, and 400 control pregnancies were analysed for the two prospective markers. Results were corrected for urine concentration by expressing marker concentrations at a fixed creatinine concentration and then expressing the results as multiples of the median for unaffected pregnancies of the same gestation. The median value of beta core in the Down's syndrome pregnancies was 2.35 compared with 2.47 for free beta hCG. Free beta hCG distributions were closely similar to those in maternal serum. Using free beta hCG, we predict Down's syndrome detection rates of 58 per cent at a 5 per cent false-positive rate. Using beta core, however, this rate fell to 41 per cent. Measurement of free beta hCG in urine may present a feasible route for screening pregnant populations, particularly where community-based obstetric care is the norm and/or if early first-trimester screening becomes a reality.
Abstract: Total human chorionic gonadotropin (hCG) levels have been shown in one previous small study to vary with gravidity. In order to establish if maternal serum free beta hCG was similarly affected, approximately 4500 pregnancies of varying gravidity were analysed. The results indicated that there was a 6 per cent higher median MOM in primigravid compared with multigravid women. The impact of such elevation in Down's syndrome screening programmes will be minimal.
Abstract: The median maternal serum free beta human chorionic gonadotropin (hCG) multiple of the median (MOM) of 480 Down syndrome cases in the second trimester was 2.64, significantly greater than the reported median MOM of intact hCG (p < 0.0001). In 234 of these cases from retrospective and prospective studies, the effectiveness of maternal serum free beta hCG was evaluated in combination with alpha-fetoprotein (AFP) and maternal age in second-trimester Down syndrome screening. Down syndrome detection in the gestational age range of 14-16 weeks was 82 per cent. In all gestational weeks (14-22), a 77.7 per cent Down syndrome detection rate was achieved. In prospective screening of 44,272 patients under the age of 35 years, 69 per cent of Down syndrome cases were detected (73 per cent in gestational weeks 14-16). The false-positive rate for the prospective study was 3.8 per cent. The use of free beta hCG combined with maternal serum AFP and maternal age-related risk for Down syndrome in a screening population (i.e., women under 35 years) yields an improved detection efficiency over other protocols.
Abstract: Since the late 1970s antenatal biochemical screening for pregnancies associated with neural tube defects has become a routine part of obstetric practice in the UK. More recently, biochemical screening programmes for chromosomal anomalies such as trisomy 21 (Down's syndrome) and trisomy 18 (Edward's syndrome) have moved on from the research stage and have begun to be implemented.
Abstract: Second-trimester distributions of the free beta human chorionic gonadotrophin (hCG) and alpha-fetoprotein (AFP) levels in 420 twin and 19 triplet pregnancies were measured and compared with the distributions in 6661 singleton pregnancies. On average, the levels of both analytes were twice as high and over three times as high in triplets. Eight sets of twins discordant for Down's syndrome showed elevated levels of free beta hCG and reduced levels of AFP after correction of the multiple of the median for the presence of a twin pregnancy. Screening for Down's syndrome using the twin correction of the multiple of the median is expected to achieve a 51 per cent detection rate at a 5 per cent false-positive rate using these two markers.
Abstract: The potential efficacy of screening for trisomy 21 in the first trimester, using maternal serum markers alpha fetoprotein, free beta human chorionic gonadotropin, unconjugated oestriol and pregnancy associated plasma protein A, was studied in an unselected population of women between the seventh and fourteenth week of gestation. Using a combination of alpha fetoprotein and free beta human chorionic gonadotropin, 53% of affected pregnancies could be identified at a false positive rate of 5%. Unconjugated oestriol and pregnancy associated plasma protein A levels were lower in cases of trisomy 21, but their inclusion with other markers did not significantly improve detection rate. Monitoring the same pregnancies also in the second trimester showed that screening in the first trimester identified the same cases as in the second. We conclude that first trimester screening using free beta human chorionic gonadotropin and alpha fetoprotein, is a viable possibility and will lead to detection rates in excess of 50%. Prospective studies are needed to confirm these observations.
Abstract: OBJECTIVE--To assess the value and impact of a screening programme for Down's syndrome that uses the two maternal serum markers: alpha fetoprotein and free beta human chorionic gonadotrophin. DESIGN--All women booked into clinics were screened. Further tests were offered to women with a risk of one in 300 or greater of having an affected baby. Follow up of outcome of all pregnancies. SETTING--Biochemical screening laboratory serving two health districts. SUBJECTS--8179 women of all ages with singleton pregnancies screened between 15 and 22 weeks' gestation from 1 April 1991 to 31 March 1992. MAIN OUTCOME MEASURES--Detection rate of Down's syndrome, false positive rate, uptake of screening, uptake of amniocentesis in women identified as at increased risk, prevalence of Down's syndrome at birth. RESULTS--Overall 89% (8317/9345) of women underwent screening. The rate of detection of Down's syndrome was 69% (11/16; 95% confidence interval 41 to 89%) with a 5.2% false positive rate (426/179; 4.7 to 5.7%). In women under 30 the detection rate was 50% (four out of eight; 32 to 86%) Uptake of amniocentesis was 89% (389/437), resulting in a reduction of prevalence of Down's syndrome at birth from 1.1 per 1000 in previous years (66/59,696) to 0.4 per 1000 during the screening year (4/9345). Additionally, several other abnormalities were identified. CONCLUSION--The benefit of a high detection rate with this approach and the additional anomalies identified should encourage others to introduce screening programmes for Down's syndrome that use free beta human chorionic gonadotrophin and alpha fetoprotein.
Abstract: OBJECTIVE--To determine the relation between maternal serum alpha fetoprotein and free beta human chorionic gonadotrophin concentrations in pregnancies complicated by trisomy 18 and establish whether prenatal biochemical screening for this condition could be developed in a way similar to that proposed for trisomy 21. DESIGN--Serum alpha fetoprotein and free beta human chorionic gonadotrophin concentrations in women with singleton pregnancies affected by cytogenetically confirmed trisomy 18, uncomplicated by neural tube defect or ventral wall defect, were identified from prospective trisomy 21 screening programmes. Additionally, stored maternal serum from similar pregnancies was analysed retrospectively. Analyte concentrations from singleton unaffected pregnancies were identified from a prospective screening programme as controls. Statistical parameters of the affected and unaffected populations were compiled. SETTING--Biochemical screening laboratories in Britain and the United States. SUBJECTS--52 women with singleton pregnancies complicated by trisomy 18; control population of 6661 women with unaffected singleton pregnancies. MAIN OUTCOME MEASURES--Median values of each analyte and their distribution in the affected and unaffected populations; detection rate of trisomy 18 and the false positive rate. RESULTS--Maternal serum alpha fetoprotein and free beta human chorionic gonadotrophin concentrations were significantly lower in pregnancies complicated by trisomy 18 (median values 0.71 and 0.37 respectively). By using a multivariate risk algorithm incorporating maternal age risk of trisomy 18 and the concentration of the two biochemical markers it was predicted that 50% of trisomy 18 cases (unaffected by neural tube defect or ventral wall defect) could be detected with a 1% false positive rate. CONCLUSION--Second trimester biochemical screening for trisomy 18 could be a valuable addition to trisomy 21 screening programmes.
Abstract: Alpha-fetoprotein (AFP), unconjugated oestriol (UE3), intact human chorionic gonadotrophin (intHCG), and the free beta subunit of chorionic gonadotrophin (F beta HCG) were investigated in a series of 21 chromosomally abnormal and 14 open neural tube defect pregnancies ascertained from a series of 14,000 prospectively collected maternal serum samples at 6-14 weeks' gestation. In 16 cases of Down's syndrome, significant reductions were found for AFP (0.65 multiples of the normal median) and UE3 (0.67 MOM). IntHCG levels were unaltered (0.97 MOM) but a significant increase was found for F beta HCG (1.96 MOM). Significant correlations were found for AFP and UE3 in the controls and for intHCG and F beta HCG in both the control and the Down's syndrome pregnancies. In a group of five trisomy 18 pregnancies, median MOMs were for AFP 0.71, for UE3 0.34, for intHCG 0.27, and for F beta HCG 0.15. None of 13 pregnancies with open neural tube defects at 8-13 weeks gestation had elevated maternal serum AFP levels, whereas matched second-trimester samples from the same pregnancies at 16-18 weeks gestation all had significantly elevated AFP levels. Thus, biochemical screening for chromosome abnormalities may be practicable in the first trimester using free beta human chorionic gonadotrophin in combination with AFP and maternal age. However, a separate screening protocol using AFP at 15-18 weeks gestation would still be required for effective detection of neural tube defects.
Abstract: We have evaluated the cross-reactivity characteristics of two distinct immunometric assays for the measurement of free beta-human chorionic gonadotropin (free beta). These maternal serum assays have been used in the initial studies which evaluated free beta as a marker in the prenatal detection of Down's syndrome. It has been suggested that free beta assays are subject to substantial potential for cross-reactivity. To confirm that free beta was the analyte responsible for enhanced detection efficiency both non-competitive and competitive cross-reactivity evaluations were undertaken. These studies demonstrated acceptably small cross-reactivity to other glycoprotein hormones or their beta components. We conclude that properly designed free beta assays will provide specific analyte measurement and improved detection efficiency in Down's syndrome screening.
Abstract: OBJECTIVE: The purpose of this study was to evaluate the potential value of maternal serum free alpha-subunit of human chorionic gonadotropin concentrations in discriminating between pregnancies associated with Down syndrome and normal matched controls. STUDY DESIGN: Maternal serum concentrations were evaluated in 36 cases of fetal Down syndrome and compared with concentrations in 180 control unaffected pregnancies within the gestational age range 16 to 20 weeks matched for maternal age, gestational age, and storage duration. RESULTS: The results of the study indicate that free alpha-subunit of human chorionic gonadotropin concentrations in the Down syndrome group were not significantly different from those in the unaffected group (median multiple of the median: for Down syndrome group, 0.991; for unaffected group, 1.000). CONCLUSION: Caution is urged in the interpretation of published data; a case for using this subunit of human chorionic gonadotropin in Down syndrome screening protocols in the second trimester is not yet proved.
Abstract: We report a multicentre clinical field trial of a novel dual analyte enzyme immunoassay method for the simultaneous measurement of alpha-fetoprotein (AFP) and free beta-human choriogonadotropin (hCG) in the same microtitre well. The assay was shown to have good technical performance in the hands of all trial centres, with between assay coefficients of variation better than 10% for both analyte across the whole of the assay ranges. The method compared well with single analyte measuring procedures and produced acceptable performance as judged by external quality assurance criteria. Recovery of added analyte and analyte dilution curves also showed acceptable performance. In clinical evaluation of a large set of neural tube defect cases, good clinical discrimination from unaffected cases was observed using AFP. With over 150 Down's syndrome cases, the combination of AFP and free beta hCG confirmed the high detection rates achievable using this marker combination, with detection rates in excess of 70% in early gestation. We conclude that the combination of clinically superior markers coupled with technologically innovative assay design will lead to more efficient Down's screening programmes.
Abstract: The role of intact, total, free alpha and free beta hCG in Down's syndrome screening is reviewed. I discuss the evidence for the enhanced detection of Down's syndrome in the second trimester using hCG beta and review the data with respect to first trimester screening with hCG subunits. I conclude that Down's syndrome screening using hCG is now well established and that increasing evidence from both retrospective and prospective studies now supports the improved detection achievable using assays that specifically measure hCG beta.
Abstract: Maternal serum free beta (hCG) levels are elevated (median 2.20 MOM) in the first trimester of pregnancy in 38 Down syndrome cases as compared with appropriate controls. This observation may form the basis for its use as a marker in screening for Down syndrome in the first trimester. Altered levels of the free beta analyte are observed in pregnancy conditions or complications other than Down syndrome.
Abstract: The use of multiple maternal serum biochemical markers in screening for Down syndrome is gaining worldwide acceptance. We sought to study the impact of the potential instability of intact human chorionic gonadotropin (hCG) on free beta-hCG subunit, a marker that has recently been used successfully in such screening. We found that, in practice, any changes in free beta-hCG due to the instability of intact hCG do not inhibit the effectiveness of free beta-hCG as a marker for Down syndrome. This was proven by controlled laboratory experiments at various stress temperatures, freeze-thaw studies, and analysis of a large set of screening data with particular reference to time in transit for individual samples. Data from controlled dissociation studies demonstrate that any apparent increase in free beta-hCG due to the instability of intact hCG cannot be attributed simply to the dissociation of intact hCG. Finally, for large-scale mass population screening in areas of the world where transport delays, safety concerns, and high temperatures preclude the shipment of liquid whole blood, dried whole-blood spots in filter paper provide a suitable delivery system with many advantages.
Abstract: A microtiter plate based Dual Analyte enzyme-immunoassay method for the simultaneous measurement of alpha-fetoprotein (AFP) and Free-beta human chorionic gonadotrophin (hCG) was evaluated. This rapid assay, which has application in both Neural Tube Defect screening and Down's screening, shows good precision with between assay coefficients of variation between 5 and 7.5% for AFP and 3.7 to 5.8% for Free-beta(hCG). Correlation with single analyte procedures is good, with correlation coefficients being greater than 0.91 in both cases. Clinical discrimination in detecting both types of abnormalities is not compromised by this new simultaneous Dual Analyte assay. We conclude that the Dual Analyte approach, which combines analytes achieving the highest known detection efficiency, will bring about improvements in the efficiency of screening, reduce costs and improve report turnaround, all leading to better quality of patient care.
Abstract: To ascertain the value of maternal serum free beta-human choriogonadotropin subunit measurement in Down's syndrome screening and to compare its effectiveness when screening with a variety of biochemical markers, we have evaluated maternal serum free beta-human choriogonadotropin, total human choriogonadotropin, alpha-fetoprotein and unconjugated oestriol in a large multicentre study of over 2800 unaffected cases and 90 affected cases, the largest collection of Down's cases ever reported. Of all the markers identified to date, free beta-human choriogonadotropin is the marker of choice for use in Down's syndrome screening. When used in early gestation (14-16 weeks) in combination with alpha-fetoprotein and maternal age, it will allow the detection of 77% of Down's cases. A side-by-side comparison with the performance of total human choriogonadotropin shows the superior detection efficiency of free beta-human choriogonadotropin. Unconjugated oestriol adds nothing further to the detection rate compared with the use of alpha-fetoprotein and free beta-human choriogonadotropin alone, and its use results in a 1% increase in false positive rate. We conclude that unconjugated oestriol has no value in Down's screening. The superior detection rate obtained using free beta-human choriogonadotropin is a result of superior detection of Down's cases in women under 30 years old, where the free beta-human choriogonadotropin combination detects 100% more cases than does the total human choriogonadotropin combination.
Abstract: In this study I investigated the analytical and clinical performance of the measurement of the free beta-subunit of choriogonadotropin (hCG) in normal pregnancies and in pregnancies affected by Down's syndrome. Free beta-hCG in maternal serum has been shown to be increased in Down's syndrome-affected pregnancies and is proportionally increased in more cases than is total hCG. This study confirms previous findings of low concentrations of unconjugated estriol and alpha-fetoprotein in maternal serum in Down's syndrome-affected pregnancies. Using a multivariate risk analysis of maternal age and concentrations of alpha-fetoprotein, unconjugated estriol, and hCG in maternal serum, I determined that, at a risk cutoff value of 1 in 300, 52% of Down's cases could be detected with total hCG in the calculation, compared with 66% with the free beta-hCG concentration. The false-positive rate was 5.9% in both cases. Therefore, free beta-hCG can be used effectively in a screening program for Down's syndrome; however, further studies are required to ascertain whether the measurement of free beta-hCG has any advantages over the use of total hCG for detecting Down's syndrome.
Abstract: Normal values for neurone specific enolase in amniotic fluid have been found to follow a non gaussian distribution with a 1-99 centile range of 1.10-4.32 micrograms/L. Neurone specific enolase levels have been shown to be raised in the amniotic fluid of pregnancies complicated by anencephaly, although not those complicated by open spina bifida. Neurone specific enolase measured by radioimmunoassay is capable of totally discriminating between normal pregnancies and those complicated by anencephaly. The study demonstrates the possible value of investigating other neuronal proteins which may find value as adjuncts to amniotic fluid Alpha fetoprotein levels in the prenatal diagnosis of Neural Tube Defects.
Abstract: The development and validation of a coated bead immunoassay for amniotic fluid acetylcholinesterase is outlined. The assay has good precision (between assay CV of 6.8% within the normal range), and is linear up to 250 arbitrary units/L. The clinical validity of this assay has been assessed using a panel of amniotic fluid samples from normal and abnormal pregnancies. At an assay cut off level of 200 arbitrary units/L, all cases of neural tube defect-affected pregnancies were identified and the number of false positives was very small. False positives resulted from severe blood staining of the amniotic fluid. Since the monoclonal antibody used recognises red cell membrane acetylcholinesterase and the stored amniotic fluids had been frozen and thawed a number of times, the extent of this problem needs to be further assessed using freshly collected samples. The performance of this assay was found to be superior to the differential inhibitor colorimetric method and close to that of the electrophoretic procedure. The quantitative nature of the assay and the independence from operator technique makes it a useful adjunct to the measurement of amniotic fluid AFP in the prenatal diagnosis of neural tube defects.
Abstract: A report was made on the outcome of a four year retrospective study in 27 064 pregnancies, of the clinical efficiency, sensitivity, and specificity of a screening programme for Down's syndrome based on reported strategies related to the measurement of maternal serum alpha fetoprotein. This study identified 27 pregnancies affected by Down's syndrome with a median multiple of the median maternal serum alpha fetoprotein concentration of 0.82. This figure is considerably higher than that obtained from previous reports on this subject. With an age related multiple of the median maternal serum alpha fetoprotein strategy, 30.8% of Down's affected pregnancies were identified as well as 11.6% of unaffected pregnancies. Perhaps a United Kingdom collaborative study should begin to investigate the reasons for such wide population variance in the reports for the median multiple of the median for Down's affected pregnancies. Until such studies are carried out, screening for Down's syndrome based on low maternal serum alpha fetoprotein concentration is premature.
Abstract: Immunonephelometric and immunoturbidimetric techniques for the measurement of proteins have developed and expanded rapidly in recent years and are fast replacing the time-honoured gel precipitation techniques. The reasons for this are primarily an increased awareness of the value of specific protein measurements with the impetus of improved chemical reagents and advances in instrument technology. This review discusses the background to such free fluid phase immunochemical measurement systems and the developments which have occurred in this field. The following topics are reviewed. (1) The theoretical background of light scattering theory as applied to the measurement of antibody-antigen complexes. (2) The nature and kinetics of the antibody-antigen reaction in fluid media and the effect of enhancing polymers. (3) The sample and antibody requirements for nephelometric and turbidimetric assay. (4) Instrumental systems for nephelometry. (5) Instrumental systems for turbidimetry. (6) Methods of establishing, assessing and monitoring nephelometric assays for specific proteins in the laboratory.
Abstract: We have developed an assay for alpha 2 macroglobulin in amniotic fluid, based on the technique of Fixed Time Kinetic Immunoturbidimetry. The assay is precise (CV 5% between assays) and has a detection limit of 0.4 mg/l. We have determined the reference range for alpha 2 macroglobulin from 100 amniotic fluid samples from none Neural Tube Defect pregnancies. The data indicates no significant variation of alpha 2 macroglobulin with gestational age and that the results in none Neural Tube Defect pregnancies showed a narrow reference range with a mean of 1.67 mg/l and -/+ 2 SD range of 0.23--3.11 mg/l (99 percentile = 3.65 mg/l). Results in 25 Neural Tube Defect pregnancies are presented.
Abstract: Five biochemical tests, which have been proposed as possible adjuncts to the measurement of amniotic fluid alphafetoprotein for the identification of neural tube defects, have been measured in 49 normal and 46 neural tube defect affected pregnancies. One test, the alphafetoprotein component non-reactive with concanavalin A, was ineffective in differentiating normal and abnormal. The remaining four procedures, the activity of acetyl and total cholinesterase, the concentration of alpha 2 macroglobulin and the electrophoretic identification of acetyl cholinesterase effectively separated the normal and abnormal populations. The relative merits of these four latter tests in the evaluation of false positive and false negative amniotic fluid alphafetoprotein results, as well as in liquor samples with high alphafetoprotein levels associated with abnormalities not of neural origin, are discussed.
Abstract: The sensitivity of kinetic immunoturbidimetry as a method for the measurement of specific proteins has been shown previously to be equivalent to 1 mg of analyte per liter. We confirm this in the method for human choriomammotropin described here. A relatively large sample volume is required, which results in other components of serum influencing the immunoprecipitin reaction. The technique is shown to be precise, and results compare well with those by a commonly available radioimmunoassay. The method performs well, as judged from results obtained for assayed quality control materials and in an external quality assurance program. The method is rapid (instrument assay time 120 s per sample), automated, and economical for routine use.
Abstract: Four methods (radioimmunoassay, electroimmunoassay, laser nephelometry and kinetic immunoturbidimetry) have been evaluated for the measurement of proteins with pregnancy-specific beta1 glycoprotein immunoreactivity. The influence of two maternal plasma proteins with different electrophoretic mobilities (alpha2 and beta1) but with similar antigenic determinants has been assessed in each assay system. The radioimmunoassay method, which utilises a homogeneous preparation of pregnancy-specific beta1 glycoprotein for the preparation of iodinated tracer, and the kinetic immunoturbidimetric assay which measures antigen-antibody complex formation over the first minute of the reaction, were both considerably more specific for the beta1 component of pregnancy specific beta1 glycoprotein immunoreactivity than the laser nephelometric or electroimmunoassay methods.
Abstract: We describe the extension of kinetic immunoturbidimetry to measurement of low-concentration proteins in serum, specifically thyroxine binding globulin. Method performance is superior to that of currently available direct assays for this protein by radioimmunoassay or the Laurell "rocket" techniques. The assay is rapid (1-min measurement period), economical, and results compare well with those by established techniques. The technique has wide applicability to instruments with kinetic measuring ability and could provide a useful support to other non-isotopic thyroid-function tests. The assay further emphasizes the sensitivity and usefulness of kinetic immunoturbidimetry for measuring low concentrations of proteins.
Abstract: The extension of kinetic immunoturbidimetry to the measurement of low concentration proteins has been described using the protein pregnancy-specific beta 1 glycoprotein. The technique has a precision superior to that of all other methods currently available. The assay is rapid, cheap and compares well with other published methods. The assay further emphasises the usefulness of the technique of kinetic immunoturbidimetry.
Abstract: A modification of a Corning-EEL 244 filter fluorimeter to take a Hellma fluoronephelometric flow cell is described, and the characteristics of a standard flow cell and the Hellma flow cell are compared by the use of a continuous flow fluorimetric calcein-calcium method. The study shows that by this modification a considerable improvement in precision, carryover, and throughput is possible. The kinetically better Hellma flow cell enables speeds in excess of 70 per hour to be achieved with carryover and precision better than that obtained at 40 per hour with the standard flow cell. Curve regeneration of signals using the Hellma flow cell can also be carried out, enabling a further increase in analytical rate to be obtained.
Abstract: In an age of reference methodologies and sophisticated quality control techniques it is surprising that so little attention is paid to the quality of the reagents that are used. This paper reports on an investigation of the bromcresol green dye-binding procedure for the estimation of serum albumin in which particular attention has been paid to changes in the reagent components that contribute to the performance of the method. It has been shown that detailed attention to the quality control of the reagents can improve the precision and interlaboratory comparison in the estimation of serum albumin.
Abstract: The measurement of sweat chloride concentration was investigated by using the Orion 417 skin chloride electrode. The effects of variation in pilocarpine concentration, iontophoresis period, and sweat collection period were also investigated. The results show that the sweat chloride concentration is directly related to the amount of sweat produced. When the amount of sweat collected falls below a certain level, there is an apparent increase in sweat chloride concentration. A procedure is recommended for the measurement of sweat chloride concentration which offers good precision (coefficient of variation 9.8%) and the minimum of inconvenience to the patient.
Abstract: Previous studies of continuous flow kinetics have described an "AutoAnalyzer" peak in terms of two time constants, lag constant "a" and exponential constant "b". Further investigations described here define some of the factors which affect these constants and hence peak shape and analytical performance. This communication outlines the application of this information to the development of an automated method for the determination of serum calcium, having a carry-over of less than 1% and an analytical rate greater than 100/hour. The instaneous colour reaction, simple hydraulics, removal of the dialysis step, and the use of an integral debubbling flow cell have enabled small kinetic constants to be achieved. Over a period of three months' routine use between-batch co-efficient of variation (C.V.) was 1.4%.
