Nyberg D A, Resta R G, Hickok D E, Hollenbach K A, Luthy D A, Mahony B S
Department of Ultrasound Medicine, Swedish Hospital Medical Center, Seattle, WA.
Am J Obstet Gynecol. 1990 May;162(5):1247-52. doi: 10.1016/0002-9378(90)90028-6.
The potential utility of screening for femur length shortening in prenatal detection of Down syndrome (trisomy 21) was evaluated by comparing 49 consecutive fetuses with Down syndrome with 572 chromosomally normal fetuses before genetic amniocentesis. Ratios of measured femur length/predicted femur length and biparietal diameter/femur length were calculated for each fetus. The predicted femur length was calculated from a regression equation relating the biparietal diameter and femur length derived from a sample control group. With this normal regression equation, 7 of 49 (14.3%) fetuses with Down syndrome had short femur lengths (measured femur length/predicted femur length ratio of less than or equal to 0.91) compared with 35 of 572 (6.1%) fetuses with a normal karyotype (p less than 0.05). However, the maximum positive predictive value for identification of Down syndrome based on short femur lengths was only 0.93% for a high-risk population (prevalence of Down syndrome, 1:250) and 0.33% for a low-risk population (prevalence of Down syndrome, 1:700). We conclude that ultrasonographic screening of short femur length is less effective for prenatal detection of Down syndrome than initially suggested.
通过在遗传羊膜穿刺术前将49例连续的唐氏综合征胎儿（21-三体）与572例染色体正常的胎儿进行比较，评估了股骨长度缩短筛查在唐氏综合征产前检测中的潜在效用。计算每个胎儿的测量股骨长度/预测股骨长度以及双顶径/股骨长度的比值。预测股骨长度由一个回归方程计算得出，该方程基于从一个样本对照组得出的双顶径与股骨长度的关系。根据这个正常回归方程，49例唐氏综合征胎儿中有7例（14.3%）股骨长度较短（测量股骨长度/预测股骨长度比值小于或等于0.91），而572例核型正常的胎儿中有35例（6.1%）股骨长度较短（p<0.05）。然而，对于高危人群（唐氏综合征患病率为1:250），基于股骨长度短来识别唐氏综合征的最大阳性预测值仅为0.93%，对于低危人群（唐氏综合征患病率为1:700）则为0.33%。我们得出结论，超声筛查股骨长度短对于唐氏综合征的产前检测效果不如最初认为的那样有效。
