Abou-Youssef Hazem S, Kamal Manal M, Mehaney Dina A
Clinical and Chemical Pathology Department, Faculty of Medicine, Cairo University, Cairo, Egypt.
PLoS One. 2014 Oct 20;9(10):e110370. doi: 10.1371/journal.pone.0110370. eCollection 2014.
The incidence of Down syndrome (DS) in Egypt varies between 1:555 and 1:770 and its screening by triple test is becoming increasingly popular nowadays. Results, however, seem inaccurate due to the lack of Egyptian-specific information needed for risk calculation and a clear policy for programme implementation. Our study aimed at calculation and validation of the triple marker medians used in screening Egyptian females as well as to recommend programme conventions to unify screening in this country.
The study was conducted on 668 Egyptian women, in weeks 15-20 of pregnancy as proven by sonar. Chorionic gonadotropin (CG), α-fetoprotein (AFP) and unconjugated oestriol (uE3) were measured on Siemens Immulite analyzer. Medians of the three parameters were calculated, regressed against gestational age (GA) and weighted by the number of participants/week. Equations were derived to adjust each parameter to the maternal weight and were centered on the median Egyptian weight. Prisca software was fed with the above data, multiples-of-median (MoM) and DS risks were calculated and the screening performance was evaluated at a mid-trimester risk cutoff of 1:270.
Log-linear [AFP/uE3 = 10(A+BGA)] and exponential equations [CG = Ae (B*GA)] were derived and the regressed medians were found to follow similar patterns to other Asian and Western medians. Oestriol was always lowest (even halved) while CG and AFP were intermediate. A linear reciprocal model best fitted weight distribution among Egyptians and successfully adjusted each parameter to a weight of 78.2 kg. Epidemiological monitoring of these recommendations revealed satisfactory performance in terms of 6.7% initial positive rate and 1.00 grand MoM.
Adoption of the above recommendations is hoped to pave the way to a successful DS screening programme tailored to Egyptian peculiarities.
埃及唐氏综合征（DS）的发病率在1:555至1:770之间，如今通过三联试验进行筛查越来越普遍。然而，由于缺乏风险计算所需的埃及特定信息以及明确的项目实施政策，结果似乎不准确。我们的研究旨在计算和验证用于筛查埃及女性的三联标志物中位数，并推荐项目规范以统一该国的筛查。
该研究对668名埃及女性进行，她们经超声证实处于妊娠15至20周。使用西门子免疫分析仪测量绒毛膜促性腺激素（CG）、甲胎蛋白（AFP）和游离雌三醇（uE3）。计算这三个参数的中位数，针对孕周（GA）进行回归，并按参与者/周的数量加权。推导方程以将每个参数调整至母亲体重，并以埃及女性体重中位数为中心。将上述数据输入Prisca软件，计算中位数倍数（MoM）和DS风险，并在孕中期风险截断值为1:270时评估筛查性能。
推导了对数线性方程[AFP/uE3 = 10(A + BGA)]和指数方程[CG = Ae (B*GA)]，发现回归后的中位数与其他亚洲和西方中位数呈现相似模式。雌三醇始终最低（甚至减半），而CG和AFP处于中间水平。线性倒数模型最适合埃及人的体重分布，并成功将每个参数调整至78.2千克的体重。对这些建议进行的流行病学监测显示，初始阳性率为6.7%，总体MoM为1.00，筛查性能令人满意。
希望采用上述建议能够为针对埃及特点的成功DS筛查项目铺平道路。
