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[Clinical evaluation of true and false positive Z values among high-risk cases screened by non-invasive prenatal
Jun Mo1, Junqing Ren, Liqian Yang
1Department of Medical Genetics and Prenatal Diagnosis, Zunyi Maternal and Child Health Care Hospital, Zunyi, Guizhou 563000, China. 273140954@qq.com.
Objective:
To analyze the Z values of true and false positive cases by non-invasive prenatal testing (NIPT) in order to improve its accuracy in clinical practice.
Methods:
Results of 24 384 NIPT tests were reviewed. For cases with high risks for trisomies 21, 18 and 13, the range of Z values in true and false positive cases was analyzed and discussed.
Results:
A total of 335 high-risk cases were identified by NIPT, among which 256 had elected prenatal diagnosis, 153 (59.77%) were verified as true positives, and 103 (40.23%) were false positives, and the area under the curve (AUC) was 0.9994. For NIPT screening, the positive predictive value (PPV) for trisomy 21 was 100% when Z>13, regardless if the pregnant woman was over 35. When 3
Conclusion:
NIPT is a technique similar to prenatal diagnosis and has a high positive predictive value for trisomies 18 and 21. Proper classification and division of the high-risk Z value of NIPT can further improve the positive predictive values for trisomies 21, 18 and 13 in different intervals, and is more helpful to guide clinicians in genetic counseling for high-risk pregnant women. Meanwhile, the compliance of prenatal diagnosis in high risk NIPT pregnant women with Z value between 3~13 was improved.
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