甲胎蛋白中位数的修正及对产前筛查效率的影响

The influence of the revised median of AFP on prenatal screening

目的：探讨产前筛查孕妇血清甲胎蛋白（AFP）中位数的修正对唐氏综合征（DS）和开放性神经管发育缺陷（NTD）筛查的影响,建立适合本实验室的甲胎蛋白中位数值.方法：采用时间分辨免疫荧光分析法对本实验室2014年1月-12月21676例孕妇血清甲胎蛋白进行检测,利用Pr-soft软件用体重进行修正,将这些数据加入到内嵌的中位数组中,与原数据库的数据一起进行曲线拟合,得到修正的中位数值.并用修正后的中位数值重新评估21676例孕妇产前筛查结果.对修正前后两组筛查的唐氏综合征和NTD的阳性率,假阳性率及阳性预测值等指标进行比较及统计分析.并对2014年数据中已确诊的25例唐氏综合征及2例漏筛病例和7例NTD阳性患者及3例漏筛病例,用修正后的中位数进行风险评估,并对评估的结果进行比较和统计分析.同时比较修正前后,各孕周中位数倍数（MoM）的变化.结果：修正中位数后2014年1月至12月唐氏综合征的确诊病例均为高风险,漏筛的2例,其中一例重新评估后为高风险,另一例依然为低风险.NTD确证病例用新中位数重新评估后均为高风险,3例漏筛病例重新评估后,其中两例为高风险,1例依旧为低风险.筛查假阳性率降低,阳性预测值及检出率提高.修正后各孕周的mMOM值在1.0±0.05附近波动.结论：建立与本实验室筛查人群及检测系统相匹配的AFP中位数值,可以有效提高筛查效率.

Objective： To explore the influence of prenatal screening pregnant women serum AFP level on Down syndrome （DS） and open neural tube defects （NTD） , and then establish the median value of AFP suitable for our laboratory. Methods： The serum AFP levels of 21676 pregnant women for prenatal screening from January 2014 to December 2014 were detected by time resolved fluoresecence irnmunoassay （TRFIA） . Correction was conducted by Pr-soft software based on weight, and add these data to embedded median value array to curve fitting together with the data from original database, and then get revised median value, which will be used to reaccess the results of 21676 cases of pregnant women prenatal screening. Comparative and statistical analysis for the positive rate, false positive rate, positive predictive value, and other indexes are preceded between the two groups before and after correction of screening for DS and NTD. The adjusted median is used for risk assessment of the data of 25 confirmed cases and 2 missed screening cases of DS and 7 NTD positive cases and 3 missed screening cases. Risk assessment is carried out with a revised median, and the results are compared and statistically analyzed. At the same time, the multiple of the median （MoM） in the gestational weeks are compared. Results： After revising median, DS from January 2014 to December 2014 is recognized as high-risk. One of the 2 missed screening cases is high-risk after reassessment while the other is still low-risk. All NTD confirmed cases are high risk after reassessment by new revised median; and among 3 missed screening cases, two of them are high-risk while the third is low-risk. False-positive rate for screening is decreased. The positive predictive value and detection rate are improved. The MOM value of each gestational week is fluctuated around 1.0±0.05. Conclusion： Establishment of AFP median matching with the screening population and detection system of our laboratory could improve the screening eflSciency.