Screening for trisomies 21 and 18 in a Spanish public hospital: from the combined test to the cell-free DNA test

Does a High-Risk (>1/50) Result for First-Trimester Combined Screening Always Entail Invasive Testing? Which Patients from This Group Might Benefit from cfDNA Testing?

Currently, cell-free DNA (cfDNA) is offered as part of a contingent screening for patients with a first-trimester combined test (FCT) risk between 1/50 and 1/250. However, most aneuploidies are within the group of patients with a risk above 1/10. An observational, retrospective, and multi-centric study was carried out, to evaluate the theorical performance of lowering the cut-off point for the high-risk group from 1/50 to 1/10. Out of the 25,920 patients included, 25,374 (97.9%) consented to the cfDNA contingent screening for aneuploidies. With the proposed strategy, knowing that the detection rate (DR) of cfDNA testing for trisomy 21 is 99.7%, the DR for trisomy 21 would have stayed in a 93.2%, just as it was with the current strategy. In this instance, 267 (1.1%) invasive tests would have been performed, while the current strategy had a total of 307 (1.2%). The false positive rate (FPR) rate would have stayed at 5.2% in both scenarios. In conclusion, the contingent screening of aneuploidies based in the result of the FCT, offering the analysis of cfDNA to patients with an intermediate risk after lowering the cut-off point from 1/50 to 1/10, is a valid alternative that might maintain the current detection rates and avoid the complications associated with invasive testing.

A Critical Evaluation of Validation and Clinical Experience Studies in Non-Invasive Prenatal Testing for Trisomies 21, 18, and 13 and Monosomy X

Non-invasive prenatal testing (NIPT) for trisomies 21, 18, 13 and monosomy X is widely utilized with massively parallel shotgun sequencing (MPSS), digital analysis of selected regions (DANSR), and single nucleotide polymorphism (SNP) analyses being the most widely reported methods. We searched the literature to find all NIPT clinical validation and clinical experience studies between January 2011 and January 2022. Meta-analyses were performed using bivariate random-effects and univariate regression models for estimating summary performance measures across studies. Bivariate meta-regression was performed to explore the influence of testing method and study design. Subgroup and sensitivity analyses evaluated factors that may have led to heterogeneity. Based on 55 validation studies, the detection rate (DR) was significantly higher for retrospective studies, while the false positive rate (FPR) was significantly lower for prospective studies. Comparing the performance of NIPT methods for trisomies 21, 18, and 13 combined, the SNP method had a higher DR and lower FPR than other methods, significantly so for MPSS, though not for DANSR. The performance of the different methods in the 84 clinical experience studies was consistent with validation studies. Clinical positive predictive values of all NIPT methods improved over the last decade. We conclude that all NIPT methods are highly effective for fetal aneuploidy screening, with performance differences across methodologies.

Clinical and Economic Evaluation after Adopting Contingent Cell-Free DNA Screening for Fetal Trisomies in South Spain

INTRODUCTION

Contingent cell-free (cf) DNA screening on the basis of the first-trimester combined test (FCT) results has emerged as a cost-effective strategy for screening of trisomy 21 (T21).

OBJECTIVES

To assess performance, patients' uptake, and cost of contingent cfDNA screening and to compare them with those of the established FCT.

METHODS

This is a prospective cohort study including all singleton pregnancies attending to their FCT for screening of T21 at 2 university hospitals in South Spain. When the FCT risk was ≥1:50, there were major fetal malformations, or the nuchal translucency was ≥3.5 mm, women were recommended invasive testing (IT); if the risk was between 1:50 and 1:270, women were recommended cfDNA testing; and for risks bellow 1:270, no further testing was recommended. Detection rate (DR), false-positive rate (FPR), patients' uptake, and associated costs were evaluated.

RESULTS

We analyzed 10,541 women, including 46 T21 cases. DR of our contingent strategy was 89.1% (41/46) at 1.4% (146/10,541) FPR. Uptake of cfDNA testing was 91.2% (340/373), and overall IT rate was 2.0%. The total cost of our strategy was €1,462,895.7, similar to €1,446,525.7 had cfDNA testing not been available.

CONCLUSIONS

Contingent cfDNA screening shows high DR, low IT rate, and high uptake at a similar cost than traditional screening.

Clinical performance of DNA-based prenatal screening using single-nucleotide polymorphisms approach in Thai women with singleton pregnancy

Background

To review the performance of noninvasive prenatal screening (NIPS) using targeted single‐nucleotide polymorphisms (SNPs) approach in mixed‐risk Thai women.

Methods

Retrospective analysis of data for detection of trisomy 21 (T21), 18 (T18), 13 (T13), monosomy X (XO), other sex chromosome aneuploidies (SCA), and triploidy/vanishing twins (VT) from a single commercial laboratory.

Results

Mean (±SD) gestational age and maternal weight were 13.2 (±2.1) weeks and 125.7 (±22.4) pounds, respectively (n = 8,572). From 462/8,572 (5.4%) no‐calls; 1/462 (0.2%) was uninformative SNPs, and 1/462 chose amniocentesis. Redraw settled 323/460 (70%) samples with low fetal fraction (FF); and 8,434/8,572 (98.4%) were finally reportable, with 131 high risks (1.6%). The median (min‐max) FF of reportable (n = 8,434) and unreportable samples (n = 137) samples were 10.5% (2.6–37.9) and 3.8% (1–14.1), respectively (p < .05). Fetal karyotypes were available in 106/131 (80.9%) and 52/138 (37.7%) high risk and repeated no‐calls, respectively. The positive predictive values (PPVs) for T21 (n = 47), T18 (n = 15), T13 (n = 7), XO (n = 8), other SCA (n = 7), and triploidy/VT were 94%, 100%, 58.3%, 66.7%, 70%, and 57.1%, respectively. None of repeated no‐calls had aneuploidies.

Conclusion

SNP‐based NIPS has high PPVs for T21 and T18. Although the proprietary SNPs library is not population‐specific, uninformative SNPs are uncommon.

Antenatal screening for fetal trisomies using microarray-based cell-free DNA testing: A systematic review and meta-analysis

OBJECTIVE

To evaluate the test accuracy of non-invasive prenatal testing (NIPT) for fetal trisomy 21, 18, and 13 using cell-free (cf) DNA analysis in maternal plasma with microarray quantitation.

METHOD

Systematic review and meta-analysis. Searches in MEDLINE, Pre-MEDLINE, EMBASE, Web of Science, and the Cochrane Library to 09.07.2018.

RESULTS

Five studies analyzing 3074 samples, including 187 trisomy 21, 43 trisomy 18, and 19 trisomy 13 cases, were identified. Risk of bias was high in all studies, introduced particularly by exclusions from analysis and by the role of the sponsor. Sensitivity of microarray-based cfDNA testing was 99.5% (95%CI 96.3%-99.9%) for trisomy 21, 97.7% (95%CI 87.9%-99.6%) for trisomy 18, and 100% (95%CI 83.2%-100%) for trisomy 13. Specificity was 100% (95% CI 99.87%-100%) for trisomy 21, 99.97% (95%CI 99.81%-99.99%) for trisomy 18, and 99.97% (95%CI 99.81%-99.99%) for trisomy 13. Pooled test failure rate was 1.1%. A direct comparison of microarray- and sequencing-based cfDNA found equivalent test accuracy.

CONCLUSION

Included studies suggest that NIPT using microarray-based cfDNA testing has high sensitivity and specificity for detecting fetal trisomy 21, 18, and 13. However, the evidence base is small and at high risk of bias.

Cell-free DNA analysis in maternal blood: comparing genome-wide versus targeted approach as a first-line screening test

Objectives: To evaluate the failure rate and performance of cell-free DNA (cfDNA) testing as a first-line screening method for major trisomies, performed by two laboratories using different analytical methods: a targeted chromosome-selective method (Harmony^® prenatal Test) versus a home-brew genome-wide (GW) massively parallel sequencing method (HB-cfDNA test), and to evaluate the clinical value of incidental findings for the latter method.Methods: CfDNA testing was performed in 3137 pregnancies with the Harmony^® prenatal Test and in 3373 pregnancies with the HB-cfDNA test. Propensity score analysis was used to match women between both groups for maternal age, weight, gestational age at testing, in vitro fertilization, rate of twin pregnancies and that of aneuploidies. Detection rates for trisomy 21 were compared between the 2 laboratories. For the HB-cfDNA test, cases with rare incidental findings were reported, including their clinical follow-up.Results: The Harmony^® prenatal Test failed at the first attempt in 90 (2.9%) of 3114 women and the HB-cfDNA test in 413 (12.2%) of 3373 women. Postmatched comparisons of the women's characteristics indicate a significantly lower failure rate in the Harmony^® group (2.8%) than in the HB cfDNA group (12.4%; p < .001). Of the 90 women in whom the Harmony^® prenatal Test failed, 61 had a repeat test, which still failed in 10, and of the 413 women in whom the HB-cfDNA test failed, 379 had a repeat test, which still failed in 110. The total failure rate after one or two attempts was therefore 1.3% (39/3114) for Harmony^® and 4.3% (144/3373) for the HB cfDNA test. After the first or second Harmony^® prenatal Test, a high-risk result was noted in 17 of the 17 cases with trisomy 21, in 5 of the seven cases with trisomy 18, and a no-call in two cases, and in the one case with trisomy 13. The respective numbers for the HB-cfDNA test are 17 of the 18 cases with trisomy 21, and a no-call in one case, 2 of the two cases with trisomy 18, and in 2 of the three cases with trisomy 13, and a no-call in one. Of the 3373 women with the HB-cfDNA test, a rare incidental finding was noted in 28 (0.8%) of the cases, of which only 2 were confirmed on amniocytes (one with microduplication 1q21.1q21.2 and one with a deletion Xp21.1), and in another case a deletion rather than a duplication of the long arm of chromosome 8 was found. In all 28 cases, there was normal clinical follow-up.Conclusions: Comparison of cfDNA testing between these two laboratories showed a four-fold lower failure rate with the Harmony^® prenatal Test, with a similar detection rate for trisomy 21. We showed no clinical relevance of disclosing additional findings beyond common trisomies with the GW HB-cfDNA test.

Has noninvasive prenatal testing impacted termination of pregnancy and live birth rates of infants with Down syndrome?

BACKGROUND

Implementation of noninvasive prenatal testing (NIPT) as a highly accurate aneuploidy screening test has raised questions around whether the high uptake may result in more terminations of pregnancies and fewer births of children with Down syndrome (DS).

AIM

The aim of the study was to investigate the impact of NIPT on termination and live birth rates for DS.

METHODS

Literature reporting pregnancy outcomes following NIPT was reviewed. Termination rates were calculated for women with a high-risk NIPT result for DS. Two audits of pregnancy outcomes where NIPT indicated DS were conducted in the United Kingdom and Singapore.

RESULTS

Fourteen studies from the United States, Asia, Europe, and the United Kingdom were included in the review. Live births of children with DS were reported in 8 studies. Termination rates following NIPT were unchanged or decreased when compared to termination rates prior to the introduction of NIPT. Audits found 15 of 43 women in the United Kingdom and 2 of 6 in Singapore continued pregnancies following a high-risk NIPT result.

CONCLUSIONS

Termination rates following the detection of DS by NIPT are unchanged or decreased compared to historical termination rates. Impact on live birth rates may be minimal in settings where termination rates fall. Population-based studies are required to determine the true impact.

The first trimester combined test for aneuploidies - a single center experience

PURPOSE

We present the results of the systematic application of the first trimester combined test for aneuploidies, in a Romanian center.

METHODS

Since October 2009, in Filantropia Hospital in Bucharest, we have systematically been using the FMF (Fetal Medicine Foundation) combined first trimester test to screen for common aneuploidies at 11 to 13 + 6 weeks of gestation. We assessed the crown to rump length (CRL), nuchal translucency, fetal heart rate as well as PAPP-A, and free β-hCG in maternal serum. We evaluated additional first trimester ultrasound markers in most of the cases. The individual risk for aneuploidies was calculated using the FMF algorithm.

RESULTS

Pregnancy outcome is known for 6030 euploid fetuses and 42 aneuploid fetuses from our screening population. The detection rate for trisomy 21 of the combined test was 87.5% for a screen positive rate of 1.96%. All of the trisomy 18 and trisomy 13 cases were detected prenatally. Some of the trisomy 18 cases proved not to be symptomatic in the first trimester.

CONCLUSIONS

Our results are similar to those of the main studies on the FMF method of first trimester screening for aneuploidies. Our numbers are small because of limited availability of the very specialized resources involved.