Johnson M P, Michaelson J E, Barr M, Treadwell M C, Isada N B, Dombrowski M P, Pryde P G, Addis J, Evans M I
Department of Obstetrics and Gynecology, Hutzel Hospital, Wayne State University, Detroit, Mich. 48201.
Fetal Diagn Ther. 1994 Mar-Apr;9(2):130-8. doi: 10.1159/000263920.
We have analyzed morphometric measurements from midgestational fetal necropsies and shown that arm and foot lengths are linear relationships versus gestational age (GA). Using foot length as the GA determinant, we found that the ratio of arm:foot length was also a linear relationship and was decreased in trisomy 21 fetuses when compared to age-matched normals. Based on these laboratory findings, we prospectively evaluated the use of the humerus:foot length ratio as a sonographic screening tool for identification of fetuses at risk for trisomy 21. Humerus length, foot length and the humerus:foot length ratio were found to be linear relationships vs. gestational age in both the normal and trisomy 21 populations. However, the regressions for the humerus:foot length ratio were significantly different between normals and Down's fetuses (p < 0.001). We found that a humerus:foot length ratio < or = 0.85 correctly identified 47% of our trisomy 21 fetuses (spec = 0.92, PPV = 0.25, NPV = 0.97). When compared to women > or = 35 years old in our high risk population, a humerus:foot length ratio < or = 0.85 carried an odds ratio of 52.7 (99% CL = 9.72-285.23) for trisomy 21.
我们分析了孕中期胎儿尸检的形态测量数据，结果显示，手臂长度和足部长度与孕龄（GA）呈线性关系。以足部长度作为孕龄的决定因素，我们发现手臂与足部长度之比同样呈线性关系，且与年龄匹配的正常胎儿相比，21三体胎儿的该比值降低。基于这些实验室研究结果，我们前瞻性地评估了肱骨与足部长度之比作为超声筛查工具用于识别21三体风险胎儿的效用。在正常胎儿和21三体胎儿群体中，肱骨长度、足部长度以及肱骨与足部长度之比均与孕龄呈线性关系。然而，正常胎儿与唐氏胎儿的肱骨与足部长度之比回归曲线存在显著差异（p < 0.001）。我们发现，肱骨与足部长度之比≤0.85可正确识别出47%的21三体胎儿（灵敏度 = 0.92，阳性预测值 = 0.25，阴性预测值 = 0.97）。在我们的高危人群中，与年龄≥35岁的女性相比，肱骨与足部长度之比≤0.85的21三体胎儿的优势比为52.7（99%置信区间 = 9.72 - 285.23）。
