建立天津地区孕中期唐氏综合征筛查人群中位数系统的研究

目的 建立天津地区孕中期唐氏综合征筛查人群中位数系统，探讨其临床应用的价值。方法 采用时间分辨荧光分析法检测100 543例妊娠14～20＋6周妊娠妇女血清甲胎蛋白（AFP）和游离绒毛促性腺激素（Free β-hCG）的浓度。利用唐氏综合征筛查风险评估软件（LC3.0）的Medians Tool统计其中61 881例不同孕周AFP和Free β-hCG的人群中位数、体质量，对LC3.0的中位数方程、体质量校正方程系数进行修正。对另外38 662例妊娠妇女AFP和Free β-hCG的中位数漂移情况进行监控及调整，建立天津地区孕中期唐氏综合征筛查人群中位数系统。另选取13 001例妊娠15～20＋6周妊娠妇女测定其AFP和 Free β-hCG激素水平，分别利用高加索人群中位数系统和已建立的人群中位数系统进行孕中期唐氏综合征筛查，设定1/270为唐氏综合征高风险切割值。≥1/270为唐氏综合征筛查高风险。并通过Medians Tool将13 001例妊娠妇女AFP和Free β-hCG的中位数，体质量与已建立的中位数曲线、体质量曲线进行拟合，检测其吻合度。结果 经染色体核型分析，13 001例妊娠妇女中共确诊唐氏综合征9例。以高加索人群中位数系统进行筛查的检出率为77.78%，假阳性率为8.30%，，阳性预测值为6.49‰。利用已建立的人群中位数系统进行筛查的检出率为77.78%，假阳性率为5.33%，阳性预测值为10.00‰。其中13001例妊娠妇女的中位数与已建立的中位数方程是吻合的，AFP和 Free β-hCG的Median Factor分别为1.01、1.00。结论 天津地区孕中期人群AFP和Free β-hCG与高加索人群存在差异，利用已建立的中位数系统进行孕中期唐氏综合征筛查，可以有效降低假阳性率，提高筛查效率。

Medians for Second-Trimester Down Syndrome Screening in Tianjin

Objective: To establish medians for second trimester Down syndrome screening in Tianjin district,and its clinical values thereof.Methods: The serum levels of maternal serum alpha-fetoprotein(AFP) and free human chorionic go nadotropin(Free β-hCG) from 113,544 pregnancies ranged from 14 weeks to 20+6 weeks were detected using time-resolved fluoroimmunoassay.The Medians Tool of the PE risk assessment software(LC3.0) was used to determine medians value of se rum AFP and free β-hCG in 61,881 pregnant women,which was modified by median coefficients,and established the Weight equation.The serum levels of AFP and free β-hCG were adjusted by median shift to establish median value system for sec ond-trimester Down syndrome screening in 38,662 pregnant women of the Tianjin area.The serum levels of AFP and free β-hCG were measured in other 13,001 pregnant women.The screening results were calculated using the standard algorithm based on the Caucasian median value system and the Tianjin median value system.Patients with an increased risk of Down syndrome pregnancy(≥270) were offered genetic amniocentesis.Results: Medians from 13,001 pregnant women matched the established median formula.The correction factors(Median factor) of AFP and free β-hCG were 1.01 and 1.00 respective ly.The detection rate(DR) of the Tianjin median value system for second-trimester Down syndrome screening was 77.78%,the false positive rate(FDR) was 5.33%,the positive predictive value was 1%,and the DR based on the Caucasian median val ue system was 77.78%,the FDR was 8.30%,the positive predictive value was 0.65%.Conclusion:Ethnic variance of mater nal serum levels of AFP and Free β-hCG exists between the Caucasian and Tianjin populations.The accuracy of screening is increased by using race-specific medians.