Screening for Down's syndrome in early and late first and second trimester using six maternal serum markers

The efficiency of six maternal serum markers for Down's syndrome (DS), alpha fetoprotein (AFP), human chorionic gonadotropin (hCG), free beta-hCG, pregnancy-associated plasma protein-A (PAPP-A), the proform of eosinophil major basic protein (ProMBP), pregnancy-specific-beta-1-glycoprotein (SP(1)), and combinations thereof, was examined. Discriminant analysis in 156 DS pregnancies and 546 controls defined three effective combinations of serum marker logMoMs (multiples of the median in control samples) in three gestational age windows, i.e. Index I (weeks 7-9) = 0.52 logMoM ProMBP + 0.28 logMoM PAPP-A - logMoM SP(1); Index II (weeks 10-12) = 1.94 logMoM free beta-hCG - logMoM SP(1), and Index III (weeks 15-19) = 0.78 logMoM free beta-hCG + 1.12 logMoM ProMBP - logMoM AFP. The estimated detection rates of indices and age for a false-positive rate (FPR) of 5% were 73% for Index I, 69% for Index II, and 60% for Index III. Including the ultrasound marker nuchal translucency, using a DS at term risk of 1 : 400 as cut-off, the detection rates of the indices increased to 86, 83, and 82% for FPRs of 4.3, 4.1, and 5.8%, respectively. The indices are promising markers for screening for DS.     

定量检测ProMBP双抗体夹心ELISA方法的建立

目的:建立定量检测ProMBP的双抗体夹心ELISA方法.方法:采用Protein A亲和层析法纯化自制的抗ProMBP单克隆抗体(mAb),并行SDS-PAGE和Western blot对纯化抗体特性进行鉴定;利用简易过碘酸钠法对抗ProMBP mAb进行标记辣根过氧化物(HRP)后行抗体配对实验;通过方阵滴定法确定包被抗体和酶标抗体的最适工作浓度;以纯化的妊娠相关血浆蛋白A(PAPP-A)/ProMBP抗原为标准品建立标准曲线;以重复性、灵敏性和回收性实验评价ELISA方法,初步对人血清中的ProMBP水平进行检测.结果:最佳配对组合为抗ProMBP mAb 4C6E5B9和HRP标记的抗ProMBP mAb 9G4A6G10,最适工作浓度分别为2.5 μg/ml和1:3 000,该方法的批内、批间变异系数分别为4.6%～6.2%和4.6%～10.5%,灵敏度达2.0 ng/ml,回收率为92%～113%.正常非妊娠血清、9～11周妊娠血清、15～17周妊娠血清ProMBP水平分别为(26.37±2.90)ng/ml、(357.71±33.60)ng/ml和(1088.77±58.13)ng/ml.结论:建立了一种可用于检测ProMBP的双抗体夹心ELISA方法.