Clinical performance of expanded non-invasive prenatal testing for aneuploidies: a real-world experience in Thailand

Data from high-income countries have shown that expanded non-invasive prenatal testing (NIPT) is highly reliable for detecting common autosomal trisomies (CATs), whereas its diagnostic accuracy for rare autosomal trisomies (RATs) remains relatively low. Information on the clinical performance of expanded NIPT in middle- and low-income countries is still limited. The objective of this study was to evaluate the clinical validity and utility of an expanded NIPT for CATs, sex chromosome aneuploidies (SCAs), and RATs following its nationwide clinical implementation. The results of NIPT were retrospectively reviewed. Those with high-risk test results were followed up via phone and/or by reviewing medical records regarding the downstream prenatal diagnosis and the pregnancy outcomes. The NIPT results of 19,714 samples were analyzed. We found screening positive rate of 0.95%; sensitivity at 97.92%, 94.12%, 85.71%, and 90% for T21, T18, T13, and SCAs; and PPV at 87.04%, 69.57%, 50%, and 54.55% for T21, T18, T13, and SCAs respectively. As for RATs, clinical validity included sensitivity at 100% and PPV of 13.3%. Over 95% of the participants with high-risk NIPT results underwent prenatal diagnosis. The majority (86.52%) of those with a confirmed diagnosis chose termination of the pregnancy. This large-scale study of mixed-risk pregnancies revealed that expanded NIPT had a good sensitivity for CATs (specifically for T21 and T18) and RATs; and fair sensitivity for T13 and SCAs. The PPV is acceptable for CATs and SCAs, but poor for RATs. These data indicated that expanded NIPT results strongly influenced pregnancy outcomes in a real-world experience.