Department of Obstetrics and Gynecology, University of Connecticut Health Center, Farmington, Connecticut USA.
J Ultrasound Med. 2013 Sep;32(9):1607-13. doi: 10.7863/ultra.32.9.1607.
The purpose of this study was to evaluate the efficacy of the genetic sonogram in Down syndrome screening for women who have received the stepwise sequential test.
This retrospective cohort study included women with singleton pregnancies who underwent stepwise sequential (first-trimester combined and second-trimester serum) screening and then had a genetic sonogram between March 2005 and January 2010. Stepwise sequential Down syndrome risks were multiplied by either a positive or negative likelihood ratio based on the second-trimester sonographic findings to determine the final Down syndrome risk. A final Down syndrome risk of 1:270 or higher was considered screen positive.
A total of 6286 women fulfilled our criteria, including 17 with Down syndrome-affected fetuses. After stepwise sequential testing, the Down syndrome detection rate was 88.2% (15 of 17), and after the genetic sonogram, there was a non-significant reduction in detection to 82.4% (14 of 17; P > .05). For the 6269 unaffected pregnancies, the genetic sonogram converted 58 screen-negative results (1%) to positive and 183 screen-positive results (3.1%) to negative. The net effect was a change in the false-positive rate from 6.2% (390 of 6269) after stepwise sequential screening to 4.2% (266 of 6269) after the genetic sonogram.
The genetic sonogram should be applied cautiously for women who have received prior prenatal screening tests. Women with screen-positive results need to be counseled that a negative sonographic result can be falsely reassuring. Conversely, for women with screen-negative results who have a risk close to the cutoff, a sonographic examination could assist in the decision of whether to accept or reject amniocentesis.
本研究旨在评估遗传超声检查在接受序贯筛查的唐氏综合征筛查中的效果。
本回顾性队列研究纳入了 2005 年 3 月至 2010 年 1 月期间接受序贯筛查（早孕期联合筛查和中孕期血清学筛查）且随后进行遗传超声检查的单胎妊娠孕妇。根据中孕期超声检查结果，将序贯筛查唐氏综合征风险乘以阳性或阴性似然比，以确定最终唐氏综合征风险。最终唐氏综合征风险≥1:270 被认为筛查阳性。
共有 6286 名孕妇符合条件，包括 17 名唐氏综合征胎儿。序贯筛查后，唐氏综合征检出率为 88.2%（15/17），遗传超声检查后检出率无显著降低，为 82.4%（14/17；P＞0.05）。对于 6269 例未受影响的妊娠，遗传超声检查将 58 例筛查阴性（1%）结果转为阳性，将 183 例筛查阳性（3.1%）结果转为阴性。其净效应是将筛查后假阳性率从序贯筛查后 6.2%（390/6269）降至遗传超声检查后 4.2%（266/6269）。
对于接受过产前筛查的孕妇，遗传超声检查的应用应谨慎。筛查阳性的孕妇需要被告知，阴性的超声结果可能会产生错误的安慰作用。相反，对于筛查阴性且风险接近截断值的孕妇，超声检查有助于决定是否接受或拒绝羊膜穿刺术。
