Ethnicity and the need for correction of biochemical and ultrasound markers of chromosomal anomalies in the first trimester: a study of Oriental, Asian and Afro-Caribbean populations

The Effect of Vanishing Twin on First- and Second-Trimester Maternal Serum Markers and Nuchal Translucency: A Multicenter Prospective Cohort Study

BACKGROUND

The purpose of this study was to evaluate the effect of vanishing twin (VT) on maternal serum marker concentrations and nuchal translucency (NT).

METHODS

This is a secondary analysis of a multicenter prospective cohort study in 12 institutions. Serum concentrations of pregnancy-associated plasma protein-A in the first trimester and alpha-fetoprotein (AFP), total human chorionic gonadotrophin, unconjugated estriol, and inhibin A in the second trimester were measured, and NT was measured between 10 and 14 weeks of gestation.

RESULTS

Among 6,793 pregnant women, 5,381 women were measured for serum markers in the first or second trimester, including 65 cases in the VT group and 5,316 cases in the normal singleton group. The cases in the VT group had a higher median multiple of the median value of AFP and inhibin A than the normal singleton group. The values of other serum markers and NT were not different between the two groups. After the permutation test with adjustment, AFP and inhibin A remained significant differences. The frequency of abnormally increased AFP was also higher in the VT group than in the normal singleton group.

CONCLUSION

VT can be considered as an adjustment factor for risk assessment in the second-trimester serum screening test.

Combinatorial Analysis of Circulating Biomarkers and Maternal Characteristics for Preeclampsia Prediction in the First and Third Trimesters in Asia

We aim to establish a prediction model for pregnancy outcomes through a combinatorial analysis of circulating biomarkers and maternal characteristics to effectively identify pregnant women with higher risks of preeclampsia in the first and third trimesters within the Asian population. A total of two hundred and twelve pregnant women were screened for preeclampsia through a multicenter study conducted in four recruiting centers in Taiwan from 2017 to 2020. In addition, serum levels of sFlt-1/PlGF ratio, miR-181a, miR-210 and miR-223 were measured and transformed into multiples of the median. We thus further developed statistically validated algorithmic models by designing combinations of different maternal characteristics and biomarker levels. Through the performance of the training cohort (0.848 AUC, 0.73−0.96 95% CI, 80% sensitivity, 85% specificity, p < 0.001) and the validation cohort (0.852 AUC, 0.74−0.98 95% CI, 75% sensitivity, 87% specificity, p < 0.001) from one hundred and fifty-two women with a combination of miR-210, miR-181a and BMI, we established a preeclampsia prediction model for the first trimester. We successfully identified pregnant women with higher risks of preeclampsia in the first and third trimesters in the Asian population using the established prediction models that utilized combinatorial analysis of circulating biomarkers and maternal characteristics.

Stability of maternal serum free β-hCG following whole blood sample transit: First trimester Down's syndrome screening in Scotland

BACKGROUND

Maternal serum free beta human chorionic gonadotrophin (free β-hCG) is used as a biomarker in first trimester screening for fetal Down's syndrome. Production of free β-hCG can occur in vitro in a time- and temperature-dependent manner; thus, the current Scottish screening protocol states samples must be received by the laboratory within 72 h. To assess the validity of the protocol, an audit was conducted to determine the impact of transit time on maternal serum free β-hCG multiple of median (MoM) values in the Scottish screened population.

METHODS

Corrected MoM values from antenatal screening carried out over one year (April 2017 to March 2018) were stratified according to sample transit time and compared. To investigate possible environmental temperature effects, the data were split according to season and maternal serum free β-hCG concentrations from summer and winter compared.

RESULTS

Of the 28,368 samples included in the study, 24,368 were received on the day of phlebotomy or after one day in transit. Only 1.5% of samples were received after 3 days in transit. The difference in maternal serum free β-hCG MoM values due to transit time was not significant. No statistical difference was found between maternal serum free β-hCG concentrations from samples collected in summer and winter months.

CONCLUSION

The current sample receipt protocol in use by the Scottish Down's syndrome screening programme is fit for purpose.

Quad test for fetal aneuploidy screening as a predictor of small-for-gestational age fetuses: a population-based study

BACKGROUND

To identify the relationship between quadruple test for aneuploidy screening (alpha-fetoprotein: AFP; free beta-human chorionic gonadotropin: b-hCG; unconjugated estriol: uE3 and inhibin-A: IHA) and fetal growth restriction and to construct predictive models for small-for-gestational-age (SGA) fetuses.

METHODS

Women who underwent quadruple test for aneuploidy were followed-up for final outcomes. The multiples of the median (MoMs) of the four biochemical markers for the SGA group and those of normal fetuses were compared. The models for predicting SGA by the individual biomarkers and their combination were constructed using binary logistic regression analysis, and their diagnostic performances in predicting SGA were determined.

RESULTS

Of 10,155 eligible pregnant women, 578 (5.7%) and 9577 (94.3%) had SGA and normal growth, respectively. High levels of AFP, b-hCG and IHA but low levels of uE3 significantly increased the risk of SGA. The constructed predictive equations had predictive performance for SGA, with areas under the receiver-operated characteristic curve of 0.724, 0.655, 0.597, 0.664 and 0.754 for AFP, b-hCG, uE3, IHA, and the combination, respectively.

CONCLUSION

The quad test for aneuploidy screening could also be used as a predictor of SGA, without extra-effort and extra-cost.

Current update of first trimester preeclampsia screening in Asia

In consideration of high prevalence of preeclampsia, enormous studies attempted to look for strategies in early gestation. Hence, a powerful screening should be built up in first trimester. Then, Aspirin could be administrated for proper prevention. The objective of this article is reviewing the screening for preeclampsia in first trimester recently. To identify the high-risk group precisely, an effective model should be recommended to Asian population. Articles related to first trimester screening of PE in Asia from databases of PubMed, ScienceDirect and Scopus were searched for this narrative review. The criteria included randomized clinical trials, observational prospective and retrospective cohort studies, case-control studies, systematic review and meta-analysis and professional review articles. Screening models combining maternal factors, biophysical factors, ultrasound studies and biochemical factors achieved high predictive performance of preeclampsia. In Asia, the detection rate of the Fetal Medicine Foundation is superior to those of the American College of Obstetricians and Gynecologists and the National Institute for Health and Care Excellence. Consequently, this effective model from the Fetal Medicine Foundation should be continuously used for screening in first trimester for the Asian.

Performance of Fetal Medicine Foundation Software for Pre-Eclampsia Prediction Upon Marker Customization: Cross-Sectional Study

Background

FMF2012 is an algorithm developed by the Fetal Medicine Foundation (FMF) to predict pre-eclampsia on the basis of maternal characteristics combined with biophysical and biochemical markers. Afro-Caribbean ethnicity is the second risk factor, in magnitude, found in populations tested by FMF, which was not confirmed in a Brazilian setting.

Objective

This study aimed to analyze the performance of pre-eclampsia prediction software by customization of maternal ethnicity.

Methods

This was a cross-sectional observational study, with secondary evaluation of data from FMF first trimester screening tests of singleton pregnancies. Risk scores were calculated from maternal characteristics and biophysical markers, and they were presented as the risk for early pre-eclampsia (PE34) and preterm pre-eclampsia (PE37). The following steps were followed: (1) identification of women characterized as black ethnicity; (2) calculation of early and preterm pre-eclampsia risk, reclassifying them as white, which generated a new score; (3) comparison of the proportions of women categorized as high risk between the original and new scores; (4) construction of the receiver operator characteristic curve; (5) calculation of the area under the curve, sensitivity, and false positive rate; and (6) comparison of the area under the curve, sensitivity, and false positive rate of the original with the new risk by chi-square test.

Results

A total of 1531 cases were included in the final sample, with 219 out of 1531 cases (14.30; 95% CI 12.5-16.0) and 182 out of 1531 cases (11.88%; 95% CI 10.3-13.5) classified as high risk for pre-eclampsia development, originally and after recalculating the new risk, respectively. The comparison of FMF2012 predictive model performance between the originally estimated risks and the estimated new risks showed that the difference was not significant for sensitivity and area under the curve, but it was significant for false positive rate.

Conclusions

We conclude that black ethnicity classification of Brazilian pregnant women by the FMF2012 algorithm increases the false positive rate. Suppressing ethnicity effect did not improve the test sensitivity. By modifying demographic characteristics, it is possible to improve some performance aspects of clinical prediction tests.

No. 261-Prenatal Screening for Fetal Aneuploidy in Singleton Pregnancies

OBJECTIVE

To develop a Canadian consensus document on maternal screening for fetal aneuploidy (e.g., Down syndrome and trisomy 18) in singleton pregnancies.

OPTIONS

Pregnancy screening for fetal aneuploidy started in the mid 1960s, using maternal age as the screening test. New developments in maternal serum and ultrasound screening have made it possible to offer all pregnant patients a non-invasive screening test to assess their risk of having a fetus with aneuploidy to determine whether invasive prenatal diagnostic testing is necessary. This document reviews the options available for non-invasive screening and makes recommendations for Canadian patients and health care workers.

OUTCOMES

To offer non-invasive screening for fetal aneuploidy (trisomy 13, 18, 21) to all pregnant women. Invasive prenatal diagnosis would be offered to women who screen above a set risk cut-off level on non-invasive screening or to pregnant women whose personal, obstetrical, or family history places them at increased risk. Currently available non-invasive screening options include maternal age combined with one of the following: (1) first trimester screening (nuchal translucency, maternal age, and maternal serum biochemical markers), (2) second trimester serum screening (maternal age and maternal serum biochemical markers), or (3) 2-step integrated screening, which includes first and second trimester serum screening with or without nuchal translucency (integrated prenatal screen, serum integrated prenatal screening, contingent, and sequential). These options are reviewed, and recommendations are made.

EVIDENCE

Studies published between 1982 and 2009 were retrieved through searches of PubMed or Medline and CINAHL and the Cochrane Library, using appropriate controlled vocabulary and key words (aneuploidy, Down syndrome, trisomy, prenatal screening, genetic health risk, genetic health surveillance, prenatal diagnosis). Results were restricted to systematic reviews, randomized controlled trials, and relevant observational studies. There were no language restrictions. Searches were updated on a regular basis and incorporated in the guideline to August 2010. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment- related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. The previous Society of Obstetricians and Gynaecologists of Canada guidelines regarding prenatal screening were also reviewed in developing this clinical practice guideline.

VALUES

The quality of evidence was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care.

BENEFITS, HARMS, AND COSTS

This guideline is intended to reduce the number of prenatal invasive procedures done when maternal age is the only indication. This will have the benefit of reducing the numbers of normal pregnancies lost because of complications of invasive procedures. Any screening test has an inherent false- positive rate, which may result in undue anxiety. It is not possible at this time to undertake a detailed cost-benefit analysis of the implementation of this guideline, since this would require health surveillance and research and health resources not presently available; however, these factors need to be evaluated in a prospective approach by provincial and territorial initiatives.

RECOMMENDATIONS

Reference centile charts of first-trimester aneuploidy screening & Doppler parameters for Indian population

Background & objectives:

The risk estimation for foetal aneuploidies in the first trimester of pregnancy uses reference curves based on western data. The objective of this study was to construct the reference curves of first-trimester foetal aneuploidy screening parameters for the Indian women.

Methods:

Cross-sectional data were obtained from 1204 singleton pregnancies between the crown-rump length (CRL) of 40-84 mm. Linear regression models were constructed; the mean, median and standard deviation were derived as a function of CRL.

Results:

The mean value of CRL was 61.3 mm. The regression analysis showed a significant correlation between all variables and CRL (P<0.001). There was a positive correlation of CRL with nuchal translucency (NT) (y=0.010x+0.629, R²=0.116) and pregnancy-associated plasma protein-A (PAPP-A) (y=0.107x−1.079, R²=0.173), whereas inverse correlation was seen with free β-human chorionic gonadotropin (β-hCG) (y=−0.409x+75.025, R²=0.018) and Doppler parameters pulsatility index (PI) (y=−0.008x+1.924 R²=0.053). The centile charts of NT, PAPP-A, free β-hCG and uterine artery (Ut A) Doppler PI were constructed.

Interpretation & conclusions:

The reference centile charts of first trimester aneuploidy screening along with Doppler parameters were derived in Indian pregnant women. These centile charts may be used as a reference for clinical use in Indian population.

Distribution of PAPP-A and total hCG between 11 and 13 weeks of gestation in Japanese pregnant women

Objectives: To establish the reference values for PAPP-A and total hCG between 11 and 13 weeks of gestation for the use of risk assessment of fetal aneuploidy in Japanese pregnant women.Methods: A multicenter prospective study was conducted. The subjects included only Japanese pregnant women with viable singleton who requested the first trimester combined (nuchal translucency and maternal serum marker) screening for fetal aneuploidy. Reference values of PAPP-A and total hCG in Japanese population were made and compared with them in Caucasian.Results: Overall 1,751 Japanese pregnant women were analyzed. Median vales of maternal serum concentration in Japanese pregnant women from 11 + 0-13 + 6 weeks' gestation were ranged from 3.01 to 9.51 mIU/mL for PAPP-A and from 70.2 to 58.3 IU/mL for total-hCG, respectively. Regression curve of median maternal serum PAPP-A and total-hCG concentration against gestational days are significantly higher in Japanese comparing with Caucasian. At most distant values, Japanese serum concentration indicated 1.45 MoM for total-hCG and 1.70 MoM for PAPP-A based on Caucasian regression curves.Conclusion: A modification of the equations by specific reference values is necessary for Japanese pregnant women at the risk assessment of chromosomal abnormalities using the first trimester maternal serum marker.

First-trimester serum biomarker screening for fetal Down syndrome as a predictor of preterm delivery: a population-based study

Objective: To examine the relationship between the first-trimester serum biomarker levels (pregnancy-associated plasma protein A:PAPP-A; and free beta-human chorionic gonadotropin: b-hCG) and preterm birth; and to create the predictive models for preterm birth in case of strong correlation.Methods: Secondary analysis on a large prospective database of singleton pregnancies undergoing first-trimester serum screening with complete follow-up for pregnancy outcomes. The multiples of medians (MoM) of the biomarkers were compared between the group of term and preterm/early preterm birth. Predictive models were developed based on adjusted MoMs and logistic regression analysis, and then diagnostic performances in predicting preterm birth were assessed.Results: Of 24,611 pregnancies eligible for analysis, 1908 (7.8%) and 500 (2.0%) had preterm and early preterm birth, respectively. Medians MoMs of both biomarkers were significantly lower in preterm and early preterm birth group. The predictive models were constructed. Performance in predicting preterm birth of these models yielded the area-under-ROC-curve of 0.560, 0.652, and 0.653 for b-hCG, PAPP-A, and combined biomarkers, respectively. In predicting early preterm birth, the areas-under-the-curve were found to be 0.551, 0.675, and 0.674 for b-hCG, PAPP-A, and combined biomarkers, respectively.Conclusion: The routine first-trimester serum screening of fetal Down syndrome could also be used as a tool of risk identification of preterm birth. We could take advantage of the screening by incorporating the predictive models into the Down syndrome screening software to report the preterm risk in the same test without extra effort and extra cost.

How to correct the impact of ethnicity on effectiveness of the second trimester maternal serum screen of fetal Down syndrome?

Objectives: To compare the performance of second trimester maternal serum screen (MSS) for fetal Down syndrome in Thai population between the conventional method using Caucasian reference ranges with ethnic factor correction (CRR-EC) and the method using specific Thai reference ranges (TRRs). Methods: A prospective database of the MSS project was accessed. The concentrations of alpha fetoprotein (AFP), beta-hCG, and uE3 were converted to their multiple of medians (MoMs) by two methods; CRR-EC for Asian women and TRR. The detection rate and false positive rate derived from the two methods were compared. Results: Of 20,229 cases, 35 women had fetal Down syndrome. The detection rates of both methods were comparable, whereas the false-positive rate of TRR was significantly lower (8.8 versus 11.7%; p < .001). The improvement was mainly caused by more accuracy of the MoMs of beta-hCG, not AFP/uE3, based on TRR. Conclusions: The effectiveness of MSS could be improved by using our own reference ranges instead of using ethnic factor correction. With TRR, the false-positive rate or the number of invasive diagnoses could be significantly decreased without compromise of the detection rate. To improve MSS performance, each population should use its own reference ranges.

Improved prediction of gestational hypertension by inclusion of placental growth factor and pregnancy associated plasma protein-a in a sample of Ghanaian women

BACKGROUND

We assessed whether adding the biomarkers Pregnancy Associated Plasma Protein-A (PAPP-A) and Placental Growth Factor (PlGF) to maternal clinical characteristics improved the prediction of a previously developed model for gestational hypertension in a cohort of Ghanaian pregnant women.

METHODS

This study was nested in a prospective cohort of 1010 pregnant women attending antenatal clinics in two public hospitals in Accra, Ghana. Pregnant women who were normotensive, at a gestational age at recruitment of between 8 and 13 weeks and provided a blood sample for biomarker analysis were eligible for inclusion. From serum, biomarkers PAPP-A and PlGF concentrations were measured by the AutoDELFIA immunoassay method and multiple of the median (MoM) values corrected for gestational age (PAPP-A and PlGF) and maternal weight (PAPP-A) were calculated. To obtain prediction models, these biomarkers were included with clinical predictors maternal weight, height, diastolic blood pressure, a previous history of gestational hypertension, history of hypertension in parents and parity in a logistic regression to obtain prediction models. The Area Under the Receiver Operating Characteristic Curve (AUC) was used to assess the predictive ability of the models.

RESULTS

Three hundred and seventy three women participated in this study. The area under the curve (AUC) of the model with only maternal clinical characteristics was 0.75 (0.64-0.86) and 0.89(0.73-1.00) for multiparous and primigravid women respectively. The AUCs after inclusion of both PAPP-A and PlGF were 0.82 (0.74-0.89) and 0.95 (0.87-1.00) for multiparous and primigravid women respectively.

CONCLUSION

Adding the biomarkers PAPP-A and PlGF to maternal characteristics to a prediction model for gestational hypertension in a cohort of Ghanaian pregnant women improved predictive ability. Further research using larger sample sizes in similar settings to validate these findings is recommended.

Prediction and prevention of pre-eclampsia in Asian subpopulation

The benefit of the early administration of aspirin to reduce preterm pre-eclampsia among screened positive European women from multivariate algorithmic approach (ASPRE trial) has opened an intense debate on the feasibility of universal screening. This review aims to assess the new perspectives in the combined screening of pre-eclampsia in the first trimester of pregnancy and the chances for prevention using low-dose aspirin with special emphasis on the particularities of the Asian population. PubMed, CENTRAL and Embase databases were searched from inception until 15 November 2017 using combinations of the search terms: preeclampsia, Asian, prenatal screening, early prediction, ultrasonography, pregnancy, biomarker, mean arterial pressure, soluble fms-like tyrosine kinase-1, placental growth factor, pregnancy-associated plasma protein-A and pulsatility index. This is not a systematic review or meta-analysis, so the risk of bias of the selected published articles and heterogeneity among the studies need to be considered. The prevalence of pre-eclampsia and serum levels of biochemical markers in Asian are different from Caucasian women; hence, Asian ethnicity needs to be corrected for in the algorithmic assessment of multiple variables to improve the screening performance. Aspirin prophylaxis may still be viable in Asian women, but resource implication needs to be considered. Asian ethnicity should be taken into account before implementing pre-eclampsia screening strategies in the region. The variables included can be mixed and matched to achieve an optimal performance that is appropriate for economical restriction in individual countries.

Low maternal serum pregnancy-associated plasma protein-A as a risk factor of preeclampsia

INTRODUCTION

Low levels of pregnancy-associated plasma protein-A (PAPP-A) might be associated with abnormal placentation, leading to the development of preeclampsia during late gestation. We aimed to determine the association between low serum PAPP-A levels and rates of preeclampsia in Thai women with otherwise low-risk pregnancies.

METHODS

A cohort study was conducted on consecutive singleton pregnancies undergoing first trimester screening for fetal Down syndrome at a tertiary centre hospital. A prospective database was assessed for patient records, including PAPP-A levels, pregnancy outcomes and obstetrics complications. Pregnancies with potential causes of preeclampsia were excluded. Enrolled women were categorised into two groups: women with normal PAPP-A levels (≥ 10th percentile; control group); and those with low PAPP-A levels (< 10th percentile; study group). The main outcome measure was rate of preeclampsia.

RESULTS

Of 6,887 women screened, 3,830 were available for analysis and 167 were excluded due to potential confounders. Of the remaining 3,663 women enrolled, 357 women were categorised as having low PAPP-A levels and 3,306 had normal PAPP-A levels. The prevalence of preeclampsia (8.4% vs. 2.6%) and early-onset preeclampsia (i.e. before 34 weeks of gestation) (1.1% vs. 0.1%) was significantly higher (relative risk 3.27 and 9.26, respectively) in women from the study group than in the control group.

CONCLUSION

Pregnancy with PAPP-A levels < 10th percentile was significantly associated with an increased risk of preeclampsia that tended toward early development. Therefore, pregnant women with low PAPP-A levels in the first trimester should be considered to be at increased risk of preeclampsia.

First trimester ultrasound tests alone or in combination with first trimester serum tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three, rather than two copies of chromosome 21; or the specific area of chromosome 21 implicated in causing Down's syndrome. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life.Non-invasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive and false negative screening tests (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first trimester ultrasound markers alone, and in combination with first trimester serum tests for the detection of Down's syndrome.

SEARCH METHODS

We carried out extensive literature searches including MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), and The Database of Abstracts of Reviews of Effects (the Cochrane Library 2011, Issue 7). We checked reference lists and published review articles for additional potentially relevant studies.

SELECTION CRITERIA

Studies evaluating tests of first trimester ultrasound screening, alone or in combination with first trimester serum tests (up to 14 weeks' gestation) for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

We included 126 studies (152 publications) involving 1,604,040 fetuses (including 8454 Down's syndrome cases). Studies were generally good quality, although differential verification was common with invasive testing of only high-risk pregnancies. Sixty test combinations were evaluated formed from combinations of 11 different ultrasound markers (nuchal translucency (NT), nasal bone, ductus venosus Doppler, maxillary bone length, fetal heart rate, aberrant right subclavian artery, frontomaxillary facial angle, presence of mitral gap, tricuspid regurgitation, tricuspid blood flow and iliac angle 90 degrees); 12 serum tests (inhibin A, alpha-fetoprotein (AFP), free beta human chorionic gonadotrophin (ßhCG), total hCG, pregnancy-associated plasma protein A (PAPP-A), unconjugated oestriol (uE3), disintegrin and metalloprotease 12 (ADAM 12), placental growth factor (PlGF), placental growth hormone (PGH), invasive trophoblast antigen (ITA) (synonymous with hyperglycosylated hCG), growth hormone binding protein (GHBP) and placental protein 13 (PP13)); and maternal age. The most frequently evaluated serum markers in combination with ultrasound markers were PAPP-A and free ßhCG.Comparisons of the 10 most frequently evaluated test strategies showed that a combined NT, PAPP-A, free ßhCG and maternal age test strategy significantly outperformed ultrasound markers alone (with or without maternal age) except nasal bone, detecting about nine out of every 10 Down's syndrome pregnancies at a 5% false positive rate (FPR). In both direct and indirect comparisons, the combined NT, PAPP-A, free ßhCG and maternal age test strategy showed superior diagnostic accuracy to an NT and maternal age test strategy (P < 0.0001). Based on the indirect comparison of all available studies for the two tests, the sensitivity (95% confidence interval) estimated at a 5% FPR for the combined NT, PAPP-A, free ßhCG and maternal age test strategy (69 studies; 1,173,853 fetuses including 6010 with Down's syndrome) was 87% (86 to 89) and for the NT and maternal age test strategy (50 studies; 530,874 fetuses including 2701 Down's syndrome pregnancies) was 71% (66 to 75). Combinations of NT with other ultrasound markers, PAPP-A and free ßhCG were evaluated in one or two studies and showed sensitivities of more than 90% and specificities of more than 95%.High-risk populations (defined before screening was done, mainly due to advanced maternal age of 35 years or more, or previous pregnancies affected with Down's syndrome) showed lower detection rates compared to routine screening populations at a 5% FPR. Women who miscarried in the over 35 group were more likely to have been offered an invasive test to verify a negative screening results, whereas those under 35 were usually not offered invasive testing for a negative screening result. Pregnancy loss in women under 35 therefore leads to under-ascertainment of screening results, potentially missing a proportion of affected pregnancies and affecting test sensitivity. Conversely, for the NT, PAPP-A, free ßhCG and maternal age test strategy, detection rates and false positive rates increased with maternal age in the five studies that provided data separately for the subset of women aged 35 years or more.

AUTHORS' CONCLUSIONS

Test strategies that combine ultrasound markers with serum markers, especially PAPP-A and free ßhCG, and maternal age were significantly better than those involving only ultrasound markers (with or without maternal age) except nasal bone. They detect about nine out of 10 Down's affected pregnancies for a fixed 5% FPR. Although the absence of nasal bone appeared to have a high diagnostic accuracy, only five out of 10 affected Down's pregnancies were detected at a 1% FPR.

First and second trimester serum tests with and without first trimester ultrasound tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three copies of chromosome 21 (or the specific area of chromosome 21 implicated in causing Down's syndrome) rather than two. It is the commonest congenital cause of mental disability. Non-invasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.  Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal) and false negative screening tests (i.e. a fetus with Down's syndrome will be missed). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first and second trimester serum markers with and without first trimester ultrasound markers for the detection of Down's syndrome in the antenatal period, as combinations of markers.

SEARCH METHODS

We conducted a sensitive and comprehensive literature search of MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), the Database of Abstracts of Reviews of Effectiveness (the Cochrane Library 25 August 2011), MEDION (25 August 2011), the Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), the National Research Register (Archived 2007), and Health Services Research Projects in Progress database (25 August 2011). We did not apply a diagnostic test search filter. We did forward citation searching in ISI citation indices, Google Scholar and PubMed 'related articles'. We also searched reference lists of retrieved articles SELECTION CRITERIA: Studies evaluating tests of combining first and second trimester maternal serum markers in women up to 24 weeks of gestation for Down's syndrome, with or without first trimester ultrasound markers, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

Twenty-two studies (reported in 25 publications) involving 228,615 pregnancies (including 1067 with Down's syndrome) were included. Studies were generally high quality, although differential verification was common with invasive testing of only high risk pregnancies. Ten studies made direct comparisons between tests. Thirty-two different test combinations were evaluated formed from combinations of eight different tests and maternal age; first trimester nuchal translucency (NT) and the serum markers AFP, uE3, total hCG, free βhCG, Inhibin A, PAPP-A and ADAM 12. We looked at tests combining first and second trimester markers with or without ultrasound as complete tests, and we also examined stepwise and contingent strategies.Meta-analysis of the six most frequently evaluated test combinations showed that a test strategy involving maternal age and a combination of first trimester NT and PAPP-A, and second trimester total hCG, uE3, AFP and Inhibin A significantly outperformed other test combinations that involved only one serum marker or NT in the first trimester, detecting about nine out of every 10 Down's syndrome pregnancies at a 5% false positive rate. However, the evidence was limited in terms of the number of studies evaluating this strategy, and we therefore cannot recommend one single screening strategy.

AUTHORS' CONCLUSIONS

Tests involving first trimester ultrasound with first and second trimester serum markers in combination with maternal age are significantly better than those without ultrasound, or those evaluating first trimester ultrasound in combination with second trimester serum markers, without first trimester serum markers. We cannot make recommendations about a specific strategy on the basis of the small number of studies available.

Observational study comparing the performance of first-trimester screening protocols for detecting trisomy 21 in a North Indian population

OBJECTIVE

To evaluate first-trimester screening protocols for detecting trisomy 21 in an Indian population.

METHODS

The present prospective study collected data from women with singleton pregnancies and a crown-to-rump length of 45-84 mm who presented at the fetal medicine unit of a tertiary care center in North India between June 1, 2006, and December 31, 2015, for combined first-trimester screening. Maternal age, nuchal translucency, nasal bone, and maternal serum levels of free beta human chorionic gonadotropin and pregnancy-associated plasma protein A were assessed for calculating the risk of trisomy 21. Tricuspid regurgitation and qualitative analysis of ductus venosus data were available from June 2010, and were included where available. Trisomy-21 detection rates were calculated for various screening protocols and were compared.

RESULTS

There were 4523 women screened and 24 records of trisomy 21. Combined screening with maternal age, nuchal translucency, nasal bone, tricuspid regurgitation, and ductus venosus demonstrated optimal detection and false-positive rates of 93.8% and 1.9%, respectively. Screening using only maternal age yielded a detection rate of 37.5%; using fixed nuchal translucency cut-off values of 2.5 and 3 mm resulted in detection rates of 66.7% and 37.5%, respectively.

CONCLUSION

Combined first-trimester screening performed well in an Indian population; combining maternal age, nuchal translucency, nasal bone, ductus venosus, and tricuspid regurgitation yielded the most accurate screening.

Pregnancy Associated Plasma Protein-A and Placental Growth Factor in a Sub-Saharan African Population: A Nested Cross-Sectional Study

Background

Baseline distributions of pregnancy disorders’ biomarkers PlGF and PAPP-A levels are primarily based on Western European populations of Caucasian ethnicity. Differences in PAPP-A and PlGF concentrations by ethnicity have been observed, with increased levels in Afro-Caribbean, East Asian, and South Asian women. Baseline concentrations of sub-Saharan African women have not been evaluated.

Objectives

To investigate PlGF and PAPP-A in a sub-Saharan African population and assess the performance of existing reference values of PAPP-A and PlGF.

Methods

A nested cross-sectional study was conducted in two public hospitals in Accra, Ghana. Out of the original 1010 women enrolled in the cohort, 398 participants were eligible for inclusion with a normotensive singleton gestation and serum samples taken between 56–97 days of pregnancy. PAPP-A and PlGF concentrations were measured with an automated immunoassay. Multiple of the median (MoM) values corrected for gestation and maternal weight for PAPP-A and PlGF were calculated using reference values of a Dutch perinatal screening laboratory based on over 10.000 samples, and PlGF manufacturer reference values, respectively.

Results

The PAPP-A median MoM was 2.34 (interquartile range (IQR) 1.24–3.97). Median PlGF MoM was 1.25 (IQR 0.95–1.80). Median MoM values for PAPP-A and PlGF tended to be slightly different for various Ghanaian ethnic subgroups.

Conclusions

PAPP-A and PlGF MoM values appear to be substantially higher in a sub-Saharan African population compared to the Caucasian or Afro-Caribbean MoM values previously reported. The difference suggests the need for a specific correction factor for this population to avoid underestimation of risk for fetal aneuploidies or placental disorders when using PAPP-A and PlGF MoM for screening purposes.

Urine tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three copies of chromosome 21, or the specific area of chromosome 21 implicated in causing Down's syndrome, rather than two. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life. The risk of a Down's syndrome affected pregnancy increases with advancing maternal age.Noninvasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing. Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive and false negative screening tests (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first and second trimester urine markers for the detection of Down's syndrome.

SEARCH METHODS

We carried out a sensitive and comprehensive literature search of MEDLINE (1980 to 25 August 2011), EMBASE (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 2011, Issue 7), MEDION (25 August 2011), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), The National Research Register (archived 2007), Health Services Research Projects in Progress database (25 August 2011). We studied reference lists and published review articles.

SELECTION CRITERIA

Studies evaluating tests of maternal urine in women up to 24 weeks of gestation for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

We extracted data as test positive or test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS (Quality Assessment of Diagnostic Accuracy Studies) criteria. We used hierarchical summary ROC (receiver operating characteristic) meta-analytical methods to analyse test performance and compare test accuracy. We performed analysis of studies allowing direct comparison between tests. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

We included 19 studies involving 18,013 pregnancies (including 527 with Down's syndrome). Studies were generally of high quality, although differential verification was common with invasive testing of only high-risk pregnancies. Twenty-four test combinations were evaluated formed from combinations of the following seven different markers with and without maternal age: AFP (alpha-fetoprotein), ITA (invasive trophoblast antigen), ß-core fragment, free ßhCG (beta human chorionic gonadotrophin), total hCG, oestriol, gonadotropin peptide and various marker ratios. The strategies evaluated included three double tests and seven single tests in combination with maternal age, and one triple test, two double tests and 11 single tests without maternal age. Twelve of the 19 studies only evaluated the performance of a single test strategy while the remaining seven evaluated at least two test strategies. Two marker combinations were evaluated in more than four studies; second trimester ß-core fragment (six studies), and second trimester ß-core fragment with maternal age (five studies).In direct test comparisons, for a 5% false positive rate (FPR), the diagnostic accuracy of the double marker second trimester ß-core fragment and oestriol with maternal age test combination was significantly better (ratio of diagnostic odds ratio (RDOR): 2.2 (95% confidence interval (CI) 1.1 to 4.5), P = 0.02) (summary sensitivity of 73% (CI 57 to 85) at a cut-point of 5% FPR) than that of the single marker test strategy of second trimester ß-core fragment and maternal age (summary sensitivity of 56% (CI 45 to 66) at a cut-point of 5% FPR), but was not significantly better (RDOR: 1.5 (0.8 to 2.8), P = 0.21) than that of the second trimester ß-core fragment to oestriol ratio and maternal age test strategy (summary sensitivity of 71% (CI 51 to 86) at a cut-point of 5% FPR).

AUTHORS' CONCLUSIONS

Tests involving second trimester ß-core fragment and oestriol with maternal age are significantly more sensitive than the single marker second trimester ß-core fragment and maternal age, however, there were few studies. There is a paucity of evidence available to support the use of urine testing for Down's syndrome screening in clinical practice where alternatives are available.

First trimester serum tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three, rather than two copies of chromosome 21; or the specific area of chromosome 21 implicated in causing Down's syndrome. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life.Noninvasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing. However, no test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

The aim of this review was to estimate and compare the accuracy of first trimester serum markers for the detection of Down's syndrome in the antenatal period, both as individual markers and as combinations of markers. Accuracy is described by the proportion of fetuses with Down's syndrome detected by screening before birth (sensitivity or detection rate) and the proportion of women with a low risk (normal) screening test result who subsequently had a baby unaffected by Down's syndrome (specificity).

SEARCH METHODS

We conducted a sensitive and comprehensive literature search of MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 25 August 2011), MEDION (25 August 2011), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), The National Research Register (Archived 2007), Health Services Research Projects in Progress database (25 August 2011). We did forward citation searching ISI citation indices, Google Scholar and PubMed 'related articles'. We did not apply a diagnostic test search filter. We also searched reference lists and published review articles.  

SELECTION CRITERIA

We included studies in which all women from a given population had one or more index test(s) compared to a reference standard (either chromosomal verification or macroscopic postnatal inspection). Both consecutive series and diagnostic case-control study designs were included. Randomised trials where individuals were randomised to different screening strategies and all verified using a reference standard were also eligible for inclusion. Studies in which test strategies were compared head-to-head either in the same women, or between randomised groups were identified for inclusion in separate comparisons of test strategies. We excluded studies if they included less than five Down's syndrome cases, or more than 20% of participants were not followed up.

DATA COLLECTION AND ANALYSIS

We extracted data as test positive or test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS (Quality Assessment of Diagnostic Accuracy Studies) criteria. We used hierarchical summary ROC meta-analytical methods or random-effects logistic regression methods to analyse test performance and compare test accuracy as appropriate. Analyses of studies allowing direct and indirect comparisons between tests were undertaken.

MAIN RESULTS

We included 56 studies (reported in 68 publications) involving 204,759 pregnancies (including 2113 with Down's syndrome). Studies were generally of good quality, although differential verification was common with invasive testing of only high-risk pregnancies. We evaluated 78 test combinations formed from combinations of 18 different tests, with or without maternal age; ADAM12 (a disintegrin and metalloprotease), AFP (alpha-fetoprotein), inhibin, PAPP-A (pregnancy-associated plasma protein A, ITA (invasive trophoblast antigen), free βhCG (beta human chorionic gonadotrophin), PlGF (placental growth factor), SP1 (Schwangerschafts protein 1), total hCG, progesterone, uE3 (unconjugated oestriol), GHBP (growth hormone binding protein), PGH (placental growth hormone), hyperglycosylated hCG, ProMBP (proform of eosinophil major basic protein), hPL (human placental lactogen), (free αhCG, and free ßhCG to AFP ratio. Direct comparisons between two or more tests were made in 27 studies.Meta-analysis of the nine best performing or frequently evaluated test combinations showed that a test strategy involving maternal age and a double marker combination of PAPP-A and free ßhCG significantly outperformed the individual markers (with or without maternal age) detecting about seven out of every 10 Down's syndrome pregnancies at a 5% false positive rate (FPR). Limited evidence suggested that marker combinations involving PAPP-A may be more sensitive than those without PAPP-A.

AUTHORS' CONCLUSIONS

Tests involving two markers in combination with maternal age, specifically PAPP-A, free βhCG and maternal age are significantly better than those involving single markers with and without age. They detect seven out of 10 Down's affected pregnancies for a fixed 5% FPR. The addition of further markers (triple tests) has not been shown to be statistically superior; the studies included are small with limited power to detect a difference.The screening blood tests themselves have no adverse effects for the woman, over and above the risks of a routine blood test. However some women who have a 'high risk' screening test result, and are given amniocentesis or chorionic villus sampling (CVS) have a risk of miscarrying a baby unaffected by Down's. Parents will need to weigh up this risk when deciding whether or not to have an amniocentesis or CVS following a 'high risk' screening test result.

Fetal sex differences in human chorionic gonadotropin fluctuate by maternal race, age, weight and by gestational age

Circulating levels of the placental glycoprotein hormone human chorionic gonadotropin (hCG) are higher in women carrying female v. male fetuses; yet, the significance of this difference with respect to maternal factors, environmental exposures and neonatal outcomes is unknown. As a first step in evaluating the biologic and clinical significance of sex differences in hCG, we conducted a population-level analysis to assess its stability across subgroups. Subjects were women carrying singleton pregnancies who participated in prenatal and newborn screening programs in CA from 2009 to 2012 (1.1 million serum samples). hCG was measured in the first and second trimesters and fetal sex was determined from the neonatal record. Multivariate linear models were used to estimate hCG means in women carrying female and male fetuses. We report fluctuations in the ratios of female to male hCG by maternal factors and by gestational age. hCG was higher in the case of a female fetus by 11 and 8% in the first and second trimesters, respectively (P<0.0001). There were small (1-5%) fluctuations in the sex difference by maternal race, weight and age. The female-to-male ratio in hCG decreased from 17 to 2% in the first trimester, and then increased from 2 to 19% in the second trimester (P<0.0001). We demonstrate within a well enumerated, diverse US population that the sex difference in hCG overall is stable. Small fluctuations within population subgroups may be relevant to environmental and physiologic effects on the placenta and can be probed further using these types of data.

Effect of ethnicity on first trimester biomarkers for combined trisomy 21 screening: results from a multicenter study in six Asian countries

OBJECTIVE

To assess differences between first trimester trisomy 21 screening markers free beta chain of the human chorionic gonadotrophin (βhCG) and pregnancy-associated plasma protein A (PAPP-A) in pregnant women of six different Asian countries (China, Indonesia, Korea, Taiwan, Thailand, and Vietnam) and compare serum levels with those in women of European countries.

METHODS

Median and multiple of median (MoM) values of free βhCG and PAPP-A were determined in more than 3000 pregnant women from the Asian countries during their first trimester of pregnancy. Differences in MoM values between a European reference group from a previous multicenter evaluation and the Asian population were evaluated. Two different types of population correction factors for T21 risk estimation were assessed.

RESULTS

An at least 10% difference of median MoMs between European and Asian PAPP-A values was found to be statistically significant (p < 0.0001). The specificity of the screening did not show a big difference in individual countries, when using the country-specific correction factor compared with the overall Asian correction factor (<1.4%).

CONCLUSIONS

The use of a correction factor is recommended based on the differences in European and Asian MoM values. Developing country-specific medians in larger study populations can help identify clinical relevant differences and give the opportunity to explore a more accurate risk calculation.

Risk of critical congenital heart defects by nuchal translucency norms

OBJECTIVE

The purpose of this study was to compare the performance of first-trimester nuchal translucency (NT) cutoff of ≥3.5 mm with NT percentiles that were calculated for crown-rump length to identify fetuses with critical congenital heart defects (CCHDs).

STUDY DESIGN

This was a population-level study of singleton pregnancies in California with NT measurements performed between 11 and 14 weeks of gestation. Eligible cases were those that resulted in live births from 2009-2010 and had information about the presence or absence of CCHDs available in the hospital discharge records through age 1 year (n = 76,089). Logistic binomial regression methods were used to compare the rate of CCHDs by an NT percentile for crown-rump length and millimeter cutpoints.

RESULTS

Compared with fetuses with an NT measurement of <90th percentile, fetuses with an NT of ≥99th percentile were >5 times as likely to have a CCHD (1.3% vs 0.2%; relative risk, 5.66; 95% confidence interval, 3.19-10.04) and fetuses with an NT measurement ≥3.5 mm were >12 times as likely to have a CCHD (2.8% vs 0.2%; relative risk, 12.28; 95% confidence interval, 5.11-29.51). NT ≥99th percentile had a sensitivity of 5.8% and a specificity of 98.9% for the detection of CCHDs compared with 2.6% and 99.8% for NT ≥3.5 mm.

CONCLUSION

Results show that NT measurements of ≥99th percentile and ≥3.5 mm are not equivalent and that substantial risk for CCHD extends to the less restrictive ≥99th percentile cutpoint. Data suggest that the use of this cutpoint compared with the current standard could double the number of CCHDs that are identified based on NT risk.

Can the quantity of cell-free fetal DNA predict preeclampsia: a systematic review

OBJECTIVE

Previous studies have demonstrated an increase in the quantity of cell-free fetal DNA (cffDNA) before the onset of preeclampsia. It would be beneficial if the quantity of cffDNA predicted preeclampsia in order to implement preventative trials and strategies to decrease maternal and fetal morbidity. Our objective was to review the literature on using cffDNA levels as a predictor of preeclampsia.

METHODS

We performed a systematic review following the Meta-analyses and Systematic Review of Observational Studies guidelines. Included studies evaluated cffDNA levels in pregnant women before the clinical onset of preeclampsia.

RESULTS

Thirteen studies met inclusion criteria. There was considerable heterogeneity between included studies, and all received a quality grade of C on the Grading of Recommendations Assessment, Development, and Evaluation scale. Of the 13 studies, 11 found an increase in cffDNA among pregnant women who subsequently developed preeclampsia. In addition, all four studies analyzing early-onset or severe preeclampsia found significantly elevated cffDNA levels prior to disease onset.

CONCLUSION

Cell-free fetal DNA quantification is a promising marker for preeclampsia prediction, especially for the development of early-onset or severe preeclampsia. However, because of the heterogeneity in published studies, a precise conclusion about the statistical and clinical relevance cannot be made.

A sensitive time-resolved fluoroimmunoassay for determination of median levels of pregnancy-associated plasma protein a in pregnant women in China

Pregnancy-associated plasma protein A (PAPP-A) is an important serum marker for first trimester screening. Its weekly median value varies with ethnicity. A one-step time-resolved fluoroimmunoassay (TRFIA) using two monoclonal antibodies against PAPP-A with Eu(3+) chelates as labels has been developed. Using the assay described here, we evaluated 5,301 normal serum samples from Chinese women at 7-13 weeks of gestation. The detection limit using this assay was 1.2 mIU/L, and the maximum detection range was up to 10,000 mIU/L. The intra-assay and inter-assay coefficients of variation were <3.0% and <5.0%, respectively, and the mean recovery rate was 98.0%. PAPP-A concentrations measured in 516 maternal serum samples correlated well with those obtained by Dissociation-Enhanced Lanthanide Fluorescent Immunoassay (DELFIA) PAPP-A assay (r=0.988, P<0.001). The medians for 7-13 weeks of maternal serum PAPP-A were higher in the women from China compared to reports from other countries. The present assay possesses accuracy and high sensitivity and exhibits great potential for the clinical analysis of PAPP-A. Our investigation on the median concentrations of PAPP-A will help establish reference values that are specific for China and study the importance of ethnic factors in biochemical screening.

Extended First-Trimester Screening Using Multiple Sonographic Markers and Maternal Serum Biochemistry: A Five-Year Prospective Study

<b><i>Objective:</i></b> To examine the performance of first-trimester screening test combining several fetal sonographic and maternal biochemical markers for major aneuploidy in a Chinese population. <b><i>Methods:</i></b> This was a prospective study performed over 5 years between January 2005 and December 2010 in Taiwan, with 20,586 cases that had a combination of a variety of sonographic markers and maternal serological β-human chorionic gonadotropin and pregnancy-associated plasma protein-A levels assessed at first trimester screening between 11⁺⁰ and 13⁺⁶ weeks of gestation. The risk of aneuploidy was calculated using algorithm software developed by Fetal Medicine Foundation, London. Fetal karyotyping was performed when the prenatal screening showed a risk of 1/300 or higher. All cases were followed for fetal outcome. <b><i>Results:</i></b> The study population was divided into four groups according to the screening strategy performed. The combination of maternal serological biochemistry and nuchal translucency measurement had a 66.7% detection rate of trisomy 21. Addition of nasal bone status increased the detection rate of trisomy 21 to 88.2%. Inclusion of tricuspid regurgitation flow showed an 87.5% detection rate of trisomy 21. Further inclusion of ductus venosus flow increased the detection rate of trisomy 21 to 100%. Incorporating more markers greatly increased the detection rate and decreased the false-positive rate (FPR). <b><i>Conclusion:</i></b> Extension of first-trimester screening to include more sonographic markers greatly increased the sensitivity and decreased FPR for detection of chromosomal abnormalities. Such screening strategy is effective in clinical practice for the Chinese ethnic population.

Accuracy of self-reported smoking status in first trimester aneuploidy screening

OBJECTIVES

To review the accuracy of self-reporting of smoking status in our first trimester screening population and to assess the levels of pregnancy-associated plasma protein-A (PAPP-A) and free-β human chorionic gonadotropin (free-hCGβ) in women who were classified for smoking status by serum cotinine concentrations and self-reporting.

METHODS

Cotinine concentration was determined in the stored serum 696 self-reported smokers and 442 self-reported non-smokers. PAPP-A and free-hCGβ multiples of the medians (MoMs) determined at screening were reverted to uncorrected for self-reported smoking status.

RESULTS

A total of 21.7% of those self-reporting as non-smokers had increased serum cotinine concentrations (using a cut-off of 13.7 ng/mL), indicating a positive smoking status. This under-reporting meant that serum PAPP-A and free-hCGβ MoMs were greater reduced in smokers classified by cotinine levels (17.2% and 9.7%) than in those classified by self-reporting (14.6% and 2.8%). Women who were classified as smokers at conception but had stopped at some time afterwards did not have significantly reduced marker MoMs to non-smokers.

CONCLUSIONS

Self-reporting results in under-representation of smoking in our population, resulting in a significant bias and inflated screen-positive rates.

First Trimester Maternal Serum Screening Using Biochemical Markers PAPP-A and Free β-hCG for Down Syndrome, Patau Syndrome and Edward Syndrome

The first trimester screening programme offers a noninvasive option for the early detection of aneuploidy pregnancies. This screening is done by a combination of two biochemical markers i.e. serum free β-human chorionic gonadotrophin (free β-hCG) and pregnancy associated plasma protein A (PAPP-A), maternal age and fetal nuchal translucency (NT) thickness at 11 + 0-13 + 6 weeks of gestation. A beneficial consequence of screening is the early diagnosis or trisomies 21, 18 and 13. At 11 + 0-13 + 6 weeks, the relative prevalence of trisomies 18 and 13 to trisomy 21 are found to be one to three and one to seven, respectively. All three trisomies are associated with increased maternal age, increased fetal NT and decreased PAPP-A, but in trisomy 21 serum free β-hCG is increased whereas in trisomies 18 and 13 free β-hCG is decreased.

Distribution of nuchal translucency thickness in Japanese fetuses

AIM

To establish reference values for the nuchal translucency (NT) thickness in Japanese fetuses.

MATERIAL AND METHODS

Ultrasonographic measurements of the crown-rump length (CRL) and NT were performed from 11 to 13 + 6 weeks of gestation in consecutive Japanese fetuses examined during prenatal visits between February 2011 and January 2012. The median, 5th and 95th percentiles of the NT thickness with 5 mm intervals of the CRL were confirmed.

RESULTS

A total of 970 cases were enrolled in the study. The median NT thickness for a CRL between 45 and 80 mm ranged from 1.2 mm to 1.9 mm, and the 95th percentile of these values ranged from 2.1 mm to 3.2 mm, respectively.

CONCLUSION

The reference values for the NT thickness in Japanese fetuses were determined. These values should be useful for fetal biometry, morphological assessment and first trimester screening for chromosomal abnormalities in Japan.

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.

Second trimester serum tests for Down's Syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three copies of chromosome 21 - or the specific area of chromosome 21 implicated in causing Down's syndrome - rather than two. It is the commonest congenital cause of mental retardation. Noninvasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.  

OBJECTIVES

To estimate and compare the accuracy of second trimester serum markers for the detection of Down's syndrome.

SEARCH METHODS

We carried out a sensitive and comprehensive literature search of MEDLINE (1980 to May 2007), EMBASE (1980 to 18 May 2007), BIOSIS via EDINA (1985 to 18 May 2007), CINAHL via OVID (1982 to 18 May 2007), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 2007, Issue 1), MEDION (May 2007), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (May 2007), The National Research Register (May 2007), Health Services Research Projects in Progress database (May 2007). We studied reference lists and published review articles.  

SELECTION CRITERIA

Studies evaluating tests of maternal serum in women at 14-24 weeks of gestation for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

Fifty-nine studies involving 341,261 pregnancies (including 1,994 with Down's syndrome) were included. Studies were generally high quality, although differential verification was common with invasive testing of only high-risk pregnancies. Seventeen studies made direct comparisons between tests. Fifty-four test combinations were evaluated formed from combinations of 12 different tests and maternal age; alpha-fetoprotein (AFP), unconjugated oestriol (uE3), total human chorionic gonadotrophin (hCG), free beta human chorionic gonadotrophin (βhCG), free alpha human chorionic gonadotrophin (αhCG), Inhibin A, SP2, CA125, troponin, pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PGF) and proform of eosinophil major basic protein (ProMBP).Meta-analysis of 12 best performing or frequently evaluated test combinations showed double and triple tests (involving AFP, uE3, total hCG, free βhCG) significantly outperform individual markers, detecting six to seven out of every 10 Down's syndrome pregnancies at a 5% false positive rate. Tests additionally involving inhibin performed best (eight out of every 10 Down's syndrome pregnancies) but were not shown to be significantly better than standard triple tests in direct comparisons. Significantly lower sensitivity occurred in women over the age of 35 years. Women who miscarried in the over 35 group were more likely to have been offered an invasive test to verify a negative screening results, whereas those under 35 were usually not offered invasive testing for a negative screening result. Pregnancy loss in women under 35 therefore leads to under ascertainment of screening results, potentially missing a proportion of affected pregnancies and affecting the accuracy of the sensitivity.

AUTHORS' CONCLUSIONS

Tests involving two or more markers in combination with maternal age are significantly more sensitive than those involving one marker. The value of combining four or more tests or including inhibin have not been proven to show statistically significant improvement. Further study is required to investigate reduced test performance in women aged over 35 and the impact of differential pregnancy loss on study findings.

Aneuploidy screening during pregnancy by a three-dimensional Advanced First Trimester Screening model: description of the AFS-3D algorithm

BACKGROUND

A novel screening method for fetal aneuploidies was developed, in which nuchal translucency (NT), pregnancy-associated plasma protein-A (PAPP-A), and free-β human chorionic gonadotropin (free-β hCG) are placed into a three-dimensional scatter plot. Likelihood ratios are directly inferred from the ratio of already observed healthy and diseased fetuses. This method is called 'Three-dimensional Advanced First trimester Screening' (AFS-3D). It was aimed to develop and test a new algorithm based on the results of previous studies.

METHODS

A new static-sized sphere model was developed. Several scaling factors of the axes and the optional application of the modifications 'simulation' (SIM) and 'empty sphere positive' were tested on 15,227 data sets. An additional examination was performed on a second collective (n = 458).

RESULTS

The application of the new AFS-3D model with static-sized spheres, a re-sampled ∆NT axis by a scaling factor of 0.125, and the application of SIM and Empty Box Positive resulted in a marked improvement of the test performance (area under curve, AUC = 0.9668). Analogous results (AUC = 0.9807) were found for the second test collective.

CONCLUSIONS

This novel approach is promising and should be tested on a larger, independent collective.

Korean-specific parameter models for calculating the risk of Down syndrome in the second trimester of pregnancy

The purpose of the current study was to propose a Korean-specific parameter set for calculating the risk of Down syndrome in the second trimester of pregnancy and to determine the screening performances of triple and quadruple tests in Korean women. Using the data on triple or quadruple screening from three hospitals in Korea during 7 yr, we re-converted the concentrations of four serum markers to multiple of median values according to gestational age and maternal weight. After re-calculating the risk of Down syndrome in each pregnancy by multiplying maternal age-specific risk by the likelihood ratio values for the serum markers, screening performances and optimal cut-off values of triple and quadruple tests were analyzed. Among 16,077 pregnancies, 23 cases had Down syndrome (1.4/1,000 deliveries). Compared to the previous program, the tests with new parameters had improved screening performance. The triple and quadruple tests had detection rates of 65.2% and 72.7%, respectively, at a false-positive rate of 5%. The optimal cut-off value for the quadruple and triple tests was 1:250. We have presented a Korean-specific parameter set for Down syndrome screening. The proposed screening test using this parameter set may improve the performance of Down syndrome screening for Korean women.

Prenatal screening for fetal aneuploidy in singleton pregnancies

OBJECTIVE

To develop a Canadian consensus document on maternal screening for fetal aneuploidy (e.g., Down syndrome and trisomy 18) in singleton pregnancies.

OPTIONS

Pregnancy screening for fetal aneuploidy started in the mid 1960s, using maternal age as the screening test. New developments in maternal serum and ultrasound screening have made it possible to offer all pregnant patients a non-invasive screening test to assess their risk of having a fetus with aneuploidy to determine whether invasive prenatal diagnostic testing is necessary. This document reviews the options available for non-invasive screening and makes recommendations for Canadian patients and health care workers.

OUTCOMES

To offer non-invasive screening for fetal aneuploidy (trisomy 13, 18, 21) to all pregnant women. Invasive prenatal diagnosis would be offered to women who screen above a set risk cut-off level on non-invasive screening or to pregnant women whose personal, obstetrical, or family history places them at increased risk. Currently available non-invasive screening options include maternal age combined with one of the following: (1) first trimester screening (nuchal translucency, maternal age, and maternal serum biochemical markers), (2) second trimester serum screening (maternal age and maternal serum biochemical markers), or (3) 2-step integrated screening, which includes first and second trimester serum screening with or without nuchal translucency (integrated prenatal screen, serum integrated prenatal screening, contingent, and sequential). These options are reviewed, and recommendations are made.

EVIDENCE

Studies published between 1982 and 2009 were retrieved through searches of PubMed or Medline and CINAHL and the Cochrane Library, using appropriate controlled vocabulary and key words (aneuploidy, Down syndrome, trisomy, prenatal screening, genetic health risk, genetic health surveillance, prenatal diagnosis). Results were restricted to systematic reviews, randomized controlled trials, and relevant observational studies. There were no language restrictions. Searches were updated on a regular basis and incorporated in the guideline to August 2010. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. The previous Society of Obstetricians and Gynaecologists of Canada guidelines regarding prenatal screening were also reviewed in developing this clinical practice guideline.

VALUES

The quality of evidence was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care.

BENEFITS, HARMS, AND COSTS

This guideline is intended to reduce the number of prenatal invasive procedures done when maternal age is the only indication. This will have the benefit of reducing the numbers of normal pregnancies lost because of complications of invasive procedures. Any screening test has an inherent false-positive rate, which may result in undue anxiety. It is not possible at this time to undertake a detailed cost-benefit analysis of the implementation of this guideline, since this would require health surveillance and research and health resources not presently available; however, these factors need to be evaluated in a prospective approach by provincial and territorial initiatives. RECOMMENDATIONS 1. All pregnant women in Canada, regardless of age, should be offered, through an informed counselling process, the option of a prenatal screening test for the most common clinically significant fetal aneuploidies in addition to a second trimester ultrasound for dating, assessment of fetal anatomy, and detection of multiples. (I-A) 2. Counselling must be non-directive and must respect a woman's right to accept or decline any or all of the testing or options offered at any point in the process. (III-A) 3. Maternal age alone is a poor minimum standard for prenatal screening for aneuploidy, and it should not be used a basis for recommending invasive testing when non-invasive prenatal screening for aneuploidy is available. (II-2A) 4. Invasive prenatal diagnosis for cytogenetic analysis should not be performed without multiple marker screening results except for women who are at increased risk of fetal aneuploidy (a) because of ultrasound findings, (b) because the pregnancy was conceived by in vitro fertilization with intracytoplasmic sperm injection, or (c) because the woman or her partner has a history of a previous child or fetus with a chromosomal abnormality or is a carrier of a chromosome rearrangement that increases the risk of having a fetus with a chromosomal abnormality. (II-2E) 5. At minimum, any prenatal screen offered to Canadian women who present for care in the first trimester should have a detection rate of 75% with no more than a 3% false-positive rate. The performance of the screen should be substantiated by annual audit. (III-B) 6. The minimum standard for women presenting in the second trimester should be a screen that has a detection rate of 75% with no more than a 5% false-positive rate. The performance of the screen should be substantiated by annual audit. (III-B) 7. First trimester nuchal translucency should be interpreted for risk assessment only when measured by sonographers or sonologists trained and accredited for this service and when there is ongoing quality assurance (II-2A), and it should not be offered as a screen without biochemical markers in singleton pregnancies. (I-E) 8. Evaluation of the fetal nasal bone in the first trimester should not be incorporated as a screen unless it is performed by sonographers or sonologists trained and accredited for this service and there is ongoing quality assurance. (II-2E) 9. For women who undertake first trimester screening, second trimester serum alpha fetoprotein screening and/or ultrasound examination is recommended to screen for open neural tube defects. (II-1A) 10. Timely referral and access is critical for women and should be facilitated to ensure women are able to undergo the type of screening test they have chosen as first trimester screening. The first steps of integrated screening (with or without nuchal translucency), contingent, or sequential screening are performed in an early and relatively narrow time window. (II-1A) 11. Ultrasound dating should be performed if menstrual or conception dating is unreliable. For any abnormal serum screen calculated on the basis of menstrual dating, an ultrasound should be done to confirm gestational age. (II-1A) 12. The presence or absence of soft markers or anomalies in the 18- to 20-week ultrasound can be used to modify the a priori risk of aneuploidy established by age or prior screening. (II-2B) 13. Information such as gestational dating, maternal weight, ethnicity, insulin-dependent diabetes mellitus, and use of assisted reproduction technologies should be provided to the laboratory to improve accuracy of testing. (II-2A) 14. Health care providers should be aware of the screening modalities available in their province or territory. (III-B) 15. A reliable system needs to be in place ensuring timely reporting of results. (III-C) 16. Screening programs should be implemented with resources that support audited screening and diagnostic laboratory services, ultrasound, genetic counselling services, patient and health care provider education, and high quality diagnostic testing, as well as resources for administration, annual clinical audit, and data management. In addition, there must be the flexibility and funding to adjust the program to new technology and protocols. (II-3B).