Evaluation of Amniocentesis Results in Patients With High-Risk Cell-Free Fetal DNA

Objectives: The present research was conducted to evaluate the accuracy of cell-free fetal DNA (cffDNA) in diagnosing chromosomal abnormalities and measure consistency in diagnostic results between this assay and amniocentesis. Materials and Methods: This retrospective observational study recruited pregnant women presenting for Down's syndrome screening. These women underwent the nuchal translucency ultrasound and their serum levels of pregnancy-associated plasma protein A and free beta-human chorionic gonadotropin were measured based on the aim of the study. Amniocentesis was administered in subjects with high or uncertain risk for fetal chromosomal abnormalities and cffDNA testing or the quadruple screen test in those with moderate risk. The women diagnosed as high-risk cases in cffDNA testing also underwent amniocentesis to confirm their diagnosis. Results: Amniocentesis showed trisomy 21 as the most prevalent chromosomal abnormality in 66 (67.3%) cases, followed by trisomy 18 in 12 (12.2%) and trisomy 13 in 7 (7.1%). False-positive cffDNA results were obtained in 8 (8.2%) cases. The coefficient of agreement between these two tests was, however, obtained as 0.845 (P<0.0001), and their results were significantly correlated with each other (chi 2=369, P<0.0001). Moreover, cffDNA was found to diagnose prenatal chromosomal abnormalities with a sensitivity of 100%, a specificity of 50%, a positive predictive value of 91.8%, and a negative predictive value of 100%. Conclusion: Given the high sensitivity of cffDNA observed in diagnosing chromosomal abnormalities, this assay can play a key role as a non-invasive procedure in prenatal diagnoses.