Grist T M, Fuller R W, Albiez K L, Bowie J D
Department of Radiology, Duke University Medical Center, Durham, NC 27710.
Radiology. 1990 Mar;174(3 Pt 1):837-9. doi: 10.1148/radiology.174.3.2137635.
After review of 461 consecutive amniocentesis examinations, 428 fetuses with normal karyotype and 13 with chromosomal abnormalities were analyzed. Six of the abnormal fetuses had trisomy 21, and seven had other chromosomal abnormalities. The ratio of measured-to-expected femur length (MFL/EFL) was determined for each fetus. The MFL/EFL values were 1.0 +/- 0.7 (mean +/- standard deviation) for the control group, 0.94 +/- 0.06 for trisomy 21 fetuses, 0.94 +/- 0.10 for non-trisomy 21 fetuses, and 0.94 +/- 0.08 for the entire group of fetuses with chromosomal abnormalities. The mean MFL/EFL value for the abnormal fetuses differed significantly from that for the control group (P less than .003). An MFL/EFL of 0.90 or less resulted in a sensitivity of 46.2% and a specificity of 94.1% for detection of all chromosomal abnormalities. For detecting trisomy 21, the sensitivity and specificity were 50% and 93.5%, respectively. Assuming a pretest probability for trisomy 21 of one in 250, an MFL/EFL of 0.90 or less resulted in a positive predictive value of 3%. It is concluded that an MFL/EFL of less than 0.90 modifies the relative risk for chromosomal abnormalities and may significantly influence the decision for amniocentesis.
在对461例连续羊膜腔穿刺检查进行回顾后，分析了428例核型正常的胎儿和13例染色体异常的胎儿。其中6例异常胎儿为21三体，7例为其他染色体异常。测定了每个胎儿的实测股骨长度与预期股骨长度之比（MFL/EFL）。对照组的MFL/EFL值为1.0±0.7（均值±标准差），21三体胎儿为0.94±0.06，非21三体胎儿为0.94±0.10，染色体异常胎儿全组为0.94±0.08。异常胎儿的平均MFL/EFL值与对照组相比有显著差异（P<0.003）。MFL/EFL为0.90或更低时，检测所有染色体异常的敏感性为46.2%，特异性为94.1%。对于检测21三体，敏感性和特异性分别为50%和93.5%。假设21三体的检测前概率为1/250，MFL/EFL为0.90或更低时，阳性预测值为3%。结论是，MFL/EFL小于0.90会改变染色体异常的相对风险，并可能显著影响羊膜腔穿刺的决策。
