Ting Hu

and 11 more

Objective: To systematically investigate the clinical utility of noninvasive prenatal screening (NIPS) commercially used for the common fetal aneuploidies as a prenatal screening tool for rare chromosome abnormalities (RCAs). Design: Prospective study. Setting: Hospital-based. Population or Sample: 528 gravidas with positive NIPS results for RCAs. Methods: Gravidas with positive NIPS results for RCAs subsequently underwent amniocentesis for single nucleotide polymorphism array (SNP-array) were recruit. The degrees of concordance between NIPS and SNP-array were classified into full concordance, partial concordance, discordance related and discordance. Main Outcome Measures: The positive predictive values (PPVs) for rare aneuploidies and segmental imbalances, while incidental findings for regions of homozygosity/uniparental disomy (ROH/UPD), were used to evaluate the performance of NIPS. Results: Of the 528 gravidas with positive NIPS results, 29.2% were confirmed with positive prenatal SNP-array results (154/528). The PPVs for rare aneuploidies and segmental imbalances were 6.1% (7/115) and 21.1% (87/413), respectively. ROH/UPDs, as incidental findings, have been identified in 9.5% (50/528) of gravidas with positive NIPS results. The PPV for clinical significant findings was 8.9% (47/528), including 7 cases with mosaic rare aneuploidies, 35 with pathogenic/likely pathogenic copy number variants, and 5 with imprinting disorders. Conclusions: NIPS commercially used for the common fetal aneuploidies yielded low PPV for rare aneuploidies, moderate PPV for segmental imbalances, and incidental findings for ROH/UPD. For the low PPV for clinical significant findings, NIPS has limited clinical utility for RCAs. Prenatal SNP-array should be regarded as the first-tier test for positive NIPS, particularly for those involved imprinted chromosomes.