Rozenberg P, Bussières L, Senat M-V
Département de Gynécologie - Obstétrique, Université Versailles - Saint-Quentin, Centre Hospitalier Poissy-Saint-Germain, 10, rue du Champ-Gaillard, BP 3082, 78303 Poissy cedex, France.
J Gynecol Obstet Biol Reprod (Paris). 2007 Apr;36(2):95-103. doi: 10.1016/j.jgyn.2006.12.021. Epub 2007 Feb 6.
Down syndrome screening has been based on second trimester maternal serum markers assay for many years. Another late strategy was based on the "genetic sonogram" performed in early second trimester in high-risk populations selected on maternal age or second trimester maternal serum markers. New strategies for Down syndrome screening have emerged over the last 10 years, with higher sensitivity and lower false-positive rates. First trimester ultrasound examination is a successful screening test; the sensitivity of nuchal translucency measurement is of 60 to 77% for a 5% false-positive rate. Combining nuchal translucency measurement with PAPP-A and free beta-hCG assay (first trimester combined screening) increases the sensitivity up to 82%. The most specific strategy is based on the integrated test, i.e., the integration of the quadruple test performed in second trimester (inhibine dimeric A, total beta-hCG, AFP, and uE3 assay) to the first trimester combined screening: for a 85% detection rate, the false-positive rate is estimated to 0.9%. However, it is ethical only with the patient agreement because it prevents access to the results of first trimester combined screening, and deprives the patient of an early diagnosis by CVS. Therefore, alternative strategies were proposed: step-wise sequential screening and contingent sequential screening. In the step-wise screening, karyotype is offered when the result of the combined test is beyond a specified threshold. If the combined test result is below this threshold, quadruple test is offered, and the final risk is calculated in the second trimester by integrating the results of the quadruple test with those of the combined test. Contingent screening also begins with the first trimester-combined test. According to its results, the patients are considered in one of the 3 following risk groups: high, intermediate, or low risk. An early karyotype is proposed to the high-risk group after combined testing. The low risk group is reassured and thus the quadruple test is not performed. The quadruple test is proposed to the intermediate risk group and final risk is calculated by the integration of the combined test result into the quadruple test result. The global detection rate of the step-wise or contingent sequential screening is estimated to 84% for a false-positive rate of 2%.
多年来，唐氏综合征筛查一直基于孕中期母体血清标志物检测。另一种晚期策略是基于在孕中期早期对根据母亲年龄或孕中期母体血清标志物选择的高危人群进行的“基因超声检查”。在过去10年中出现了唐氏综合征筛查的新策略，具有更高的灵敏度和更低的假阳性率。孕早期超声检查是一种成功的筛查测试；颈部透明带测量的灵敏度在假阳性率为5%时为60%至77%。将颈部透明带测量与妊娠相关血浆蛋白A和游离β-人绒毛膜促性腺激素检测（孕早期联合筛查）相结合，可将灵敏度提高至82%。最具特异性的策略基于综合检测，即在孕早期联合筛查中加入孕中期进行的四联检测（抑制素二聚体A、总β-人绒毛膜促性腺激素、甲胎蛋白和游离雌三醇检测）：在检测率为85%时，假阳性率估计为0.9%。然而，只有在患者同意的情况下才符合伦理，因为它会阻止获取孕早期联合筛查的结果，并使患者无法通过绒毛取样进行早期诊断。因此，提出了替代策略：逐步序贯筛查和偶然序贯筛查。在逐步筛查中，如果联合检测结果超过指定阈值，则提供核型分析。如果联合检测结果低于该阈值，则进行四联检测，并在孕中期通过将四联检测结果与联合检测结果相结合来计算最终风险。偶然筛查也从孕早期联合检测开始。根据检测结果，患者被分为以下三个风险组之一：高风险、中风险或低风险。联合检测后，向高风险组建议进行早期核型分析。低风险组得到安心，因此不进行四联检测。向中风险组建议进行四联检测，并通过将联合检测结果纳入四联检测结果来计算最终风险。逐步或偶然序贯筛查的总体检测率估计为84%，假阳性率为2%。
