Benefits of contingent screening vs primary screening by cell-free DNA testing: think again

The role of ultrasound in first-trimester screening after the introduction of NIPT as a service of public health insurance - a consensus statement of the Fetal Medicine Foundation (FMF) Germany

Combined first-trimester screening (FTS) and noninvasive prenatal testing (NIPT) have been proven to be reliable noninvasive procedures to detect the most common chromosomal abnormalities (trisomies 21, 18, 13) in the first trimester. The aim of this paper is to demonstrate the strengths and limitations of these two procedures and to give a consensus statement of the Fetal Medicine Foundation (FMF) Germany on how to use the two techniques in the first trimester after the introduction of NIPT as a service of the statutory health insurance companies in Germany.

Impact of cell-free fetal DNA on invasive prenatal diagnostic tests in a real-world public setting

Objective To evaluate the impact of cell-free fetal DNA (cfDNA) test on the number of invasive tests carried out in a public hospital that does not include this test in its services. Methods This was a retrospective cohort study in singleton pregnancies with a high risk (>1:270) on the first-trimester screening for aneuploidies. The options of performing an invasive test or a cfDNA test were explained to all women, the latter being especially recommended to those with a 1:50-1:270 risk (Group 1). If the risk was >1:50 (Group 2), or nuchal translucency (NT) was >99th percentile or there were major malformations (Group 3), invasive test was recommended. Results A total of 755 of 14,398 (5.2%) cases had a high-risk first-trimester screening, of whom 46 cases were excluded due to incomplete follow-up. In the remaining 709 cases, the percentage of aneuploidies was 9.9% (70 cases) and 110 opted for a cfDNA test (15.5%). There were two true-positive results of cfDNA (one in Group 2 and another in Group 3). In Group 1, 67.4% [95% confidence interval (CI) 60.0%-72.1%, P < 0.01] fewer invasive procedures were performed in those who opted for a cfDNA test, without having false negatives. Conclusion Pregnant women with a 1:50-1:270 risk who opt for cfDNA save two out of three invasive tests, without affecting the aneuploidy detection rate.

First-trimester risk assessment based on ultrasound and cell-free DNA vs combined screening: a randomized controlled trial

OBJECTIVE

This was a randomized controlled trial to compare risk assessment by first-trimester combined screening (FTCS) with an approach that combines a detailed ultrasound examination at 11-13 weeks' gestation and cell-free DNA (cfDNA) analysis.

METHODS

Pregnant women with a normal first-trimester ultrasound examination at 11-13 weeks' gestation (fetal nuchal translucency (NT) ≤ 3.5 mm and no fetal defects) were randomized into one of two groups. In the first group, risk of aneuploidy was assessed using FTCS based on the most recent UK Fetal Medicine Foundation algorithm. In the second group, risk assessment was based on ultrasound findings and cfDNA analysis. An additional tube of blood was collected for FTCS in case the cfDNA analysis was uninformative. Primary outcome was false-positive rate in screening for trisomy 21. A case was considered false positive if the karyotype was not trisomy 21 and if the risk for trisomy 21 was >1:100, irrespective of the method of risk calculation. Results were compared using 95% CIs using the Clopper-Pearson method.

RESULTS

Between October 2015 and December 2016, 1518 women with singleton pregnancy underwent first-trimester screening. Thirty-one (2.0%) pregnancies were not eligible for randomization due to increased NT (> 3.5 mm) and/or fetal defect. After exclusion of women who declined randomization (n = 87) and cases of fetal death and loss to follow-up (n = 24), 688 pregnancies were randomized into the FTCS arm and 688 into the ultrasound + cfDNA analysis arm. There were no differences in maternal and gestational age, maternal weight and BMI, ethnicity, use of assisted reproduction and cigarette smoking between the two arms. In the ultrasound + cfDNA analysis arm, median risk for trisomy 21 was 1 in 10 000. None of the cases had a risk above 1: 100 (95% CI, 0.0-0.5%). In the FTCS arm, the median risk for trisomy 21 was 1 in 3787 and in 17 cases, the risk was higher than 1:100, which corresponds to 2.5% (95% CI, 1.5-3.9%) of the FTCS study-arm population.

CONCLUSION

Our study has shown that first-trimester risk assessment for trisomy 21 that includes a detailed ultrasound examination as well as NT measurement and is followed by cfDNA testing is associated with a significant reduction in the false-positive rate compared with FTCS. This approach obviates the need for maternal serum free β-human chorionic gonadotropin and pregnancy-associated plasma protein-A in screening for fetal aneuploidy. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.