Modified multiple marker aneuploidy screening as a primary screening test for preeclampsia.

BACKGROUND: Abnormal levels of maternal biochemical markers used in multiple marker aneuploidy screening have been associated with adverse pregnancy outcomes. This study aims to assess if a combination of maternal characteristics and biochemical markers in the first and second trimesters can be used to screen for preeclampsia (PE). The secondary aim was to assess this combination in identifying pregnancies at risk for gestational hypertension and preterm birth. METHODS: This case-control study used information on maternal characteristics and residual blood samples from pregnant women who have undergone multiple marker aneuploidy screening. The median multiple of the median (MoM) of first and second trimester biochemical markers in cases (women with PE, gestational hypertension and preterm birth) and controls were compared. Biochemical markers included pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PlGF), human chorionic gonadotropin (hCG), alpha feto-protein (AFP), unconjugated estriol (uE3) and Inhibin A. Logistic regression analysis was used to estimate screening performance using different marker combinations. Screening performance was defined as detection rate (DR) and false positive rate (FPR). Preterm and early-onset preeclampsia PE were defined as women with PE who delivered at < 37 and < 34 weeks of gestation, respectively. RESULTS: There were 147 pregnancies with PE (81 term, 49 preterm and 17 early-onset), 295 with gestational hypertension, and 166 preterm birth. Compared to controls, PE cases had significantly lower median MoM of PAPP-A (0.77 vs 1.10, p < 0.0001), PlGF (0.76 vs 1.01, p < 0.0001) and free-ß hCG (0.81 vs. 0.98, p < 0.001) in the first trimester along with PAPP-A (0.82 vs 0.99, p < 0.01) and PlGF (0.75 vs 1.02, p < 0.0001) in the second trimester. The lowest first trimester PAPP-A, PlGF and free ß-hCG were seen in those with preterm and early-onset PE. At a 20% FPR, 67% of preterm and 76% of early-onset PE cases can be predicted using a combination of maternal characteristics with PAPP-A and PlGF in the first trimester. The corresponding DR was 58% for gestational hypertension and 36% for preterm birth cases. CONCLUSIONS: Maternal characteristics with first trimester PAPP-A and PlGF measured for aneuploidy screening provided reasonable accuracy in identifying women at risk of developing early onset PE, allowing triage of high-risk women for further investigation and risk-reducing therapy. This combination was less accurate in predicting women who have gestational hypertension or preterm birth.

Prenatal screening for trisomy 21: a comparative performance and cost analysis of different screening strategies.

BACKGROUND: Prenatal screening for chromosome aneuploidies have constantly been evolving, especially with the introduction of cell-free fetal DNA (cfDNA) screening in the most recent years. This study compares the performance, costs and timing of test results of three cfDNA screening implementation strategies: contingent, reflex and primary. METHODS: We modelled enhanced first trimester screening (eFTS) as the first-tier test in contingent or reflex strategies. cfDNA test was performed contingent on or reflex from eFTS results. A comparison was made between cfDNA screening using sequencing technology and Rolling Circle Amplification (RCA)/imaging solution. All model assumptions were based on results from previous publications or information from the Ontario prenatal screening population. RESULTS: At an eFTS risk cut-off of ≥1/1000, contingent and reflex cfDNA screening have the same detection rate (DR) (94%) for trisomy 21. Reflex cfDNA screening using RCA/Imaging solution provided the lowest false positive rate and cost. The number of women requiring genetic counselling and diagnostic testing was significantly reduced and women received their cfDNA screening result 9 days sooner compared with the contingent model. While primary cfDNA screening improved the trisomy 21 DR by 3-5%, it was more costly and more women required diagnostic testing. CONCLUSION: Reflex cfDNA screening is the most cost-effective prenatal screening strategy. It can improve the efficiency of prenatal aneuploidy screening by reducing the number of patient visits and providing more timely results.

Enhanced First Trimester Aneuploidy Screening with Placental Growth Factor and Alpha Feto-Protein: Detection of Trisomies 18 and 13.

OBJECTIVES: To assess the performance of first trimester combined screening (FTS) when enhanced with placental growth factor and alpha feto-protein in the detection of trisomies 18 and 13. METHODS: A retrospective case-control study. Marker parameters were derived using frozen serum samples. Multivariate Gaussian modelling predicted the detection rate (DR) and false-positive rate (FPR) for trisomies 18 and 13 with FTS and enhanced first trimester screening (eFTS) using the risk of trisomy 21 alone and an additional risk cut-off for trisomy 18, or trisomies 18 or 13. RESULTS: There were 83 trisomy 18, 22 trisomy 13, and 588 controls. The median placental growth factor levels in trisomies 18 and 13 were 0.75 and 0.65 multiple of the median of controls, respectively (both P < 0.0001). There were no statistically significant differences in alpha feto-protein levels. Modelling predicts that using a trisomy 21 risk cut-off alone, at FPR of 3%, eFTS increases the DR for trisomies 18 and 13 by 0.6-0.8% compared with FTS. Additionally using a trisomy 18 risk cut-off, at an extra FPR of 0.2%, eFTS increased the DR by 0.6-0.9% over FTS; using a trisomy 18 or 13 risk cut-off did not further increase detection for FTS or eFTS. The increase in DR was greater at higher FPR. CONCLUSION: eFTS increases the detection of trisomies 18 and 13 to a small extent.

First and second trimester maternal serum markers in pregnancies with a vanishing twin.

OBJECTIVE: The aim of this study was to assess the concentration of the first and second trimester maternal serum markers in pregnancies with a vanishing twin. METHODS: This is a retrospective case-control study of pregnancies screened for Down syndrome in one Ontario center. Singleton pregnancies with ultrasound evidence of a vanishing twin were identified, and each was matched with five normal singleton controls for ethnicity, maternal age, gestational age, and blood sampling date. The median MoM of the first and second trimester serum markers was compared between cases and controls. The differences were assessed using the Mann-Whitney U-test. RESULTS: The study included 174 pregnancies that had a vanishing twin. Compared with control pregnancies, pregnancy associated plasma protein A increased by 21% (p = 0.0026), alpha-fetoprotein (AFP) increased by 10% (p < 0.0001), and dimeric inhibin A (DIA) increased by 13% (p = 0.0470) in pregnancies with a vanishing twin. Unconjugated oestriol and total human chorionic gonadotrophin were not significantly changed in these pregnancies. CONCLUSIONS: Pregnancy associated plasma protein A is not an adequate marker for pregnancies with a vanishing twin. The impact of elevated AFP on risk estimation is offset by that of DIA to certain extent. Further studies are needed to establish an adequate adjustment method for AFP and DIA to improve the accuracy of screening results for these pregnancies.

First trimester screening for Down syndrome using nuchal translucency, maternal serum pregnancy-associated plasma protein A, free-ß human chorionic gonadotrophin, placental growth factor, and α-fetoprotein.

OBJECTIVE: The aim of this study was to assess the screening performance for Down syndrome using first trimester combined screening (FTS) and two additional markers, serum placental growth factor (PlGF) and α-fetoprotein (AFP). METHODS: This is a retrospective case-control study of 137 pregnancies affected by Down syndrome and 684 individually matched unaffected pregnancies. Stored serum samples were tested for all four markers, and results were expressed as multiples of the gestation-specific median (MoM). Multivariate Gaussian modeling was used to calculate risks for different combinations of markers and to predict the detection rate (DR) and false positive rate (FPR). The predicted performance of enhanced FTS (FTS plus PlGF and AFP) was compared with FTS; the performance without nuchal translucency (first trimester quad) was assessed. RESULTS: For affected pregnancies, the median PlGF level was 0.622 MoM and median AFP 0.764 MoM. Adding PlGF and AFP improved the screening performance. At 3% FPR, DR increased by 4.4% from 83.8% to 88.2% using enhanced FTS; at 95% DR, FPR decreased by 8.3%, from 19.3% to 11.0%. At 3% FPR, DR using first trimester quad test was 76.4%. CONCLUSIONS: The performance of FTS can be enhanced by adding PlGF and AFP. Even without nuchal translucency, the test would perform well.

The impact of maternal weight discrepancies on prenatal screening results for Down syndrome.

OBJECTIVE: This study aimed to assess the quantitative impact of maternal weight discrepancy on the screen result for Down syndrome when using Integrated Prenatal Screening and First Trimester Combined Screening. METHODS: The study population consisted of 78,165 women undergoing prenatal screening in Ontario, Canada, and 158 pregnancies affected with Down syndrome at one Ontario center. The study assessed quantitative alterations of the multiple of the median values of first and second-trimester serum markers and the risks of Down syndrome at a set of theoretical weight discrepancies. RESULTS: Weight discrepancies have the greatest impact on screening results when the initial risk is close to the risk cut-off. When the weight discrepancy is 5 lb or greater and the denominator of the initial risk is within 50 of the risk cut-off, the chance that a screen result will change from positive to negative or from negative to positive is 47-55% for women undertaking Integrated Prenatal Screening. This chance is 33-43% for women undertaking First Trimester Combined Screening. CONCLUSION: A weight discrepancy of five or more pounds has a significant impact on the risk of Down syndrome; correction of maternal weight would improve the accuracy of the screening test.

Prenatal screening for preeclampsia: the roles of placental growth factor and pregnancy-associated plasma protein A in the first trimester and placental growth factor and soluble fms-like tyrosine kinase 1-placental growth factor ratio in the early second trimester.

BACKGROUND: Professional societies have recommended universal first trimester screening for preeclampsia and a second or third trimester soluble fms-like tyrosine kinase-1-placental growth factor ratio test to assess for preeclampsia and its severity. However, it may not be feasible to implement the most optimal screening protocol for preeclampsia in the first trimester which uses a combination of maternal characteristics, maternal biophysical and biochemical markers due to limitations in the access to uterine artery doppler ultrasound. There are inconsistent findings on how early in the second trimester the fms-like tyrosine kinase-1-placental growth factor ratio begins to provide useful information in preeclampsia prediction. OBJECTIVE: This study aimed to assess the accuracy of (1) a combination of maternal characteristics, maternal serum pregnancy-associated plasma protein A, and placental growth factor in the screening for preeclampsia in the first trimester; and (2) placental growth factor or soluble fms-like tyrosine kinase-1-placental growth factor ratio in the prediction of preeclampsia in the early second trimester. STUDY DESIGN: This retrospective case-control study used frozen residual blood samples from women who had aneuploidy screening and delivered at a tertiary center. The case group included pregnancies with gestational hypertension or preeclampsia (further classified as early-onset [birth at <34 weeks' gestation] and preterm preeclampsia [birth at <37 weeks' gestation]). Each case was matched with 3 control pregnancies by date of blood sample draw, gestational age at first blood sample draw, maternal age, maternal ethnicity, type of multiple-marker screening, and amount of residual sample. Mann-Whitney U tests were used to assess the associations between serum markers and the risk of preeclampsia. Logistic regressions were used to assess if the risk of preeclampsia can be predicted using a combination of maternal characteristics and serum markers. RESULTS: The case group included 146 preeclampsia and 295 gestational hypertension cases. Compared with the controls, preeclampsia cases had significantly lower first-trimester pregnancy-associated plasma protein A and placental growth factor. At a 20% false-positive rate, 71% of early-onset and 58% of preterm preeclampsia cases can be predicted using maternal characteristics, pregnancy-associated plasma protein A, and placental growth factor. Preeclampsia cases had lower second-trimester placental growth factor and a higher soluble fms-like tyrosine kinase-1-placental growth factor ratio. At a 10% false-positive rate, 80% and 53% of early-onset preeclampsia can be predicted using maternal characteristics and placental growth factor or soluble fms-like tyrosine kinase-1-placental growth factor ratio, respectively. CONCLUSION: The current first-trimester aneuploidy screening programs may be expanded to identify women at increased risk of developing preeclampsia. Early in the second trimester, placental growth factor alone provided better prediction for preeclampsia compared with the soluble fms-like tyrosine kinase-1-placental growth factor ratio.

Standardized Procedural Practices of the Ontario Prenatal Screening Program for aneuploidies and open neural tube defects.

BACKGROUND/OBJECTIVES: The Ontario Prenatal Screening Program (OPSP) follows internationally recognized standardized procedures for laboratories and genetics clinics. However, it has been found that some procedures are subject to interpretation, so the current procedures are designed to facilitate a unified approach in the interpretation of literature recommendations. In Ontario, the OPSP offers multiple screening modalities with integrated prenatal screening (including both first and second trimester markers) being the most commonly chosen option. Other screening modalities include first trimester screening, second trimester quad screening, serum integrated screening, and NT-Quad. METHODS: The standardization was based on a literature review and on current practices in Ontario. RESULTS/DISCUSSION: The main finding of the review was a paucity of published data relating to the procedures and the decision-making processes involved in prenatal screening. The purpose of this publication is to provide the most up-to-date and pertinent information for clinical laboratory professionals involved with prenatal screening for Down syndrome, trisomy 18 and open neural tube defects.