Caughey Aaron B, Lyell Deirdre J, Washington A Eugene, Filly Roy A, Norton Mary E
Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, 94080, USA.
Prenat Diagn. 2006 Jan;26(1):22-7. doi: 10.1002/pd.1319.
To determine the number of Down syndrome (DS) fetuses identified, amniocenteses performed, and procedure-related losses incurred when second-trimester ultrasound is used to screen high-risk patients in order to determine who should undergo an amniocentesis.
A decision analytic model was designed for women at increased risk for a DS fetus due to either advanced maternal age (AMA) or a positive expanded maternal serum alpha fetoprotein (MSAFP) screening test, also known as a triple screen (+triple) test. The model compared: (1) the current standard of offering all at-risk women amniocentesis to (2) a policy of performing amniocentesis only when sonographic markers of DS are seen on ultrasound. Baseline assumptions included a sensitivity of 60.6% for targeted ultrasound and a screen-positive rate of 16.2%.
If targeted ultrasound is used to determine whether high-risk patients should undergo amniocentesis, 56% (3933/7025) of all DS fetuses are missed. The diagnosis of DS is missed most frequently among women at highest risk for DS (AMA and +triple). In this subgroup of patients, there are 3152 DS fetuses in the second trimester, of which 2815 (89%) are identified by triple screen test. When an ultrasound screen is added, only 1709 (54%) of DS fetuses will be identified.
Substantially fewer DS fetuses will be detected when targeted ultrasound is used as a screen among already identified high-risk patients.
确定在使用孕中期超声对高危患者进行筛查以确定哪些人应接受羊膜腔穿刺术时，所识别出的唐氏综合征（DS）胎儿数量、进行的羊膜腔穿刺术数量以及与操作相关的损失。
针对因母亲年龄偏大（AMA）或母亲血清甲胎蛋白（MSAFP）筛查试验结果呈阳性（即三联筛查阳性）而胎儿患DS风险增加的女性，设计了一个决策分析模型。该模型比较了：（1）对所有高危女性进行羊膜腔穿刺术的现行标准与（2）仅在超声检查中发现DS的超声标志物时才进行羊膜腔穿刺术的策略。基线假设包括针对性超声检查的敏感性为60.6%，筛查阳性率为16.2%。
如果使用针对性超声检查来确定高危患者是否应接受羊膜腔穿刺术，那么所有DS胎儿中有56%（3933/7025）会被漏诊。DS诊断在DS风险最高的女性（AMA和三联筛查阳性）中漏诊最为频繁。在该亚组患者中，孕中期有3152例DS胎儿，其中2815例（89%）通过三联筛查试验得以识别。当增加超声筛查时，只有1709例（54%）DS胎儿会被识别。
在已确定的高危患者中，将针对性超声检查用作筛查手段时，检测到的DS胎儿数量会大幅减少。
