Clinical performance of non-invasive prenatal testing in 7 707 pregnancies

Objective To evaluate the performance of non-invasive prenatal testing (NIPT) in assessing the genetic risk of a fetal chromosomal abnormality in 7 707 pregnancies. Methods Totally 8 410 NIPT results collected from the clinical laboratory of Chinese PLA General Hospital from January 2016 to June 2018 were retrospectively analyzed.Outcomes of follow-up or prenatal diagnosis were obtained in 7 707 cases.The data were grouped according to maternal age and screening indications.Amniocentesis was used as gold standard for prenatal test.The positive predictive value (PPV),negative predictive value (NPV),sensitivity,specificity,false positive rate (FPR) and false negative rate (FNR) of NIPT were compared between different groups. Results Twenty-eight high risk results by NIPT were found in the 2 978 pregnancies in elder group (≥35 years),and 21 were confirmed by amniocentesis,with high-risk rate of 0.94% (28/2 978),and PPV of 75%,NPV of 100%,sensitivity of 100%,specificity of 99.76%;48 high risk results by NIPT were found in the 4 729 cases of the younger age group (<35 years) including 28 cases confirmed by amniocentesis;with high-risk rate of 1.02% (48/4 729)(PPV:60.87%,NPV:99.96%,sensitivity:93.33%,specificity:99.62%);no significant differences was found in each index between the two groups (all P>0.05).There were 591 cases diagnosed as high risk and 1 480 as intermediate risk by traditional screening,and the prenatal diagnosis quantity decreased from 591 to 15 by NIPT second-screening,which included 10 true positive cases confirmed by amniocentesis and 5 false-positive cases. Conclusion NIPT is the optimal selection for prenatal screening of trisomy 21,trisomy 18 and trisomy 13 chromosome aneuploidies,which is beneficial to all pregnant women who choose NIPT as the first selection or second selection after the traditional test.