摘要目的:探讨无创产前检测(non-invasive prenatal testing，NIPT)筛查高风险中真假阳性中的 Z值，旨在提高实践中的NIPT准确性。 方法:收集NIPT成功的标本共计24 384例，对NIPT筛查提示为T21/T18/T13高风险的病例，分析探讨其确诊后真阳性与假阳性中 Z值判定范围。 结果:本次NIPT共筛查出高风险共计335例，其中256例选择进行产前诊断，真阳性153例(59.77%)，假阳性103例(40.23%)，AUC达到0.9994。NIPT筛查提示21三体高风险时，当 Z>13时，无论孕妇年龄是否大于35岁，本实验室检测数据阳性预测值均为100%，当3 < Z < 13时，若孕妇预产年龄为35岁及以上，NIPT筛查阳性预测值为80%(8/10)，若孕妇预产年龄为35岁以下，阳性预测值为41.6%(5/12)。NIPT筛查提示18三体高风险时，当 Z值> 13，阳性预测值为100%， Z值为3 < Z < 13时，阳性预测值仅为14.3%(1/7)。NIPT筛查提示13三体高风险时，当 Z值> 20，阳性预测值为100%， Z值为3 < Z < 20时，阳性预测值仅为6.67%(1/15)。 结论:NIPT是一项近似产前诊断类的技术，对T21、T18都有较高的阳性预测值。对NIPT高风险的 Z值进行适当分类及划分能进一步提高T21、T18、T13在不同区间内的阳性预测值，同时更利于指导临床医师对高风险孕妇进行遗传咨询，同时提升NIPT高风险孕妇 Z值在3~13之间时进行产前诊断的依从性。

abstractsObjective: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 < Z < 13, the PPV for trisomy 21 was 80% (8/10) for those > 35 and about 41.6% (5/12) for those < 35. For trisomy 18, the PPV was 100% when Z > 13, and only 14.3% (1/7) when 3 < Z < 13. NIPT showed that the positive predictive value of trisomy 13 was only 6.67% (1/15) when the trisomy 13 Z value was more than 20, the positive predictive value was 100% , and the trisomy 13 Z value was 3 < Z < 20. 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.