Non-invasive prenatal cell-free fetal DNA testing for down syndrome and other chromosomal abnormalities

Abstract

Background: Chorionic villus sampling and amniocentesis as definitive diagnostic procedures represent a gold standard for prenatal diagnosis of chromosomal abnormalities. The methods are invasive and lead to a miscarriage and fetal loss in approximately 0.5-1 %. Non-invasive prenatal DNA testing (NIPT) is based on the analysis of free-cell fetal DNA from maternal blood. It represents a highly accurate screening test for detecting the most common fetal chromosomal abnormalities. In our study we present the results of NIPT testing in the Diagnostic Center Strah, Slovenia, over the last 3 years. Methods: In our study, 123 pregnant women from 11th to 18th week of pregnancy were included. All of them had First trimester assessment of risk for trisomy 21, done before NIPT testing. Results: 5 of total 6 high-risk NIPT cases (including 3 cases of Down syndrome and 2 cases of Klinefelter’s syndrome) were confirmed by fetal karyotyping. One case-Edwards syndrome was false positive. Patau syndrome, triple X syndrome or Turner syndrome were not observed in any of the cases. Furthermore, there were no false negative cases reported. In general, NIPT testing had 100 % sensitivity (95 % confidence interval: 46.29 %-100.00 %) and 98.95 % specificity (95 % confidence interval: 93.44 %-99.95 %). In determining Down syndrome alone, specificity (95 % confidence interval: 95.25 %-100.00 %) and sensitivity (95 % confidence interval: 31.00 %-100.00 %) turned out to be 100 %. In 2015, the average turnaround time for analysis was 8.3 days from the day when the sample was taken. Repeated blood sampling was required in 2 cases (redraw rate = 1.6 %). Conclusions: Our results confirm that NIPT represents a fast, safe and highly accurate advanced screening test for most common chromosomal abnormalities. In current clinical practice, NIPT would significantly decrease the number of unnecessary invasive procedures and the rate of fetal loss caused by invasive diagnostics.