Screening for fetal chromosomal anomalies using cell free DNA at a tertiary care centre

Abstract

Aim of the study:To Evaluate the usefulness and reliability of cell free DNA as a screening method to identify the mothers at risk of fetus with trisomy 21, 18, 13, sex chromosomal anomalies and other chromosomal abnormalities. Method: This is a prospective observational study conducted at Chalmeda Anand Rao Institute of Medical Sciences, Karimnagar from a period of October 2020 to October 2022. Patients were included with at least one atypical biochemical marker of first trimester screening test or with abnormal NT scan. The cell free DNA was analysed by VeriSeq NIPT Solution v2 method. The accuracy of cell free DNA assay was evaluated by calculation of sensitivity and specificity. Screen positive cases were validated by comparing with karyotyping analysis. Results: Among the 250 patients with atypical biochemical markers who underwent a cell free DNA analysis, fourteen (5.6%) were excluded because of loss to follow-up, mis-carriage and affordability constraints. Out of 236, Cell free DNA was positive for Trisomy 21 in 3 pregnant women (n = 3), Trisomy 18 in 1 pregnant woman (n = 1) and Sex Chromosomal Aneuploidy in 1 pregnant woman (n = 1) and negative in 227 pregnant women. Test failure occurred for two pregnant women (0.8%). Conclusion:Cell free DNA assay is an effective and reliable tool in screening for fetal chromosomal anomalies.