Noninvasive Fetal Trisomy Test (NIFTY): A Large-Scale Clinical Practice in 78,289 cases. F. Chen, XY. Pan, XC. Li, HJ. Ge, SP. Chen, H. Jiang BGI-shenzhen, Shenzhen, Guangdong, China.

   Objectives To report the performance of noninvasive fetal trisomy test based on massively parallel sequencing (MPS) from maternal plasma in a large-scale clinical practice in China.
    Methods The noninvasive fetal trisomy test (NIFTY) was offered as a prenatal screening test in 49 medical centers. Participants received NIFTY as well as prenatal screening for Downs syndrome based on maternal serum and ultrasound were recruited from December 2010. Performance of NIFTY and prenatal screening was compared, and pregnancies with full karyotyping were used to evaluate sensitivity and specificity of NIFTY in trisomy 21, 18 and 13. Follow-up investigation was accessed after the expected date of confinement to offer a complete understanding.
   Results Among 78,289 cases recruited, 53,477 were at high risk for Downs syndrome according to maternal serum and ultrasound screening, while only 510 of which were identified as trisomy 21 in NIFTY. In 2125 cases with full karyotyping, 419 were classified as positive in NIFTY, including 320 cases of trisomy 21, 79 cases of trisomy 18 and 20 cases of trisomy 13, with 98.97% sensitivity and 98.10% specificity for all three trisomies. During follow-up investigation, fetal outcome of 21,839 cases without karyotyping were obtained, providing a consistent result with NIFTY identification.
   Conclusions Our large-scale clinical practice proved that MPS-based test is of high sensitivity and specificity in detecting fetal common trisomies. Compared to traditional prenatal screening, this MPS-based test could avoid about 99.05% of invasive prenatal diagnostic procedures.

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