Bork M D, Egan J F, Cusick W, Borgida A F, Campbell W A, Rodis J F
Department of Obstetrics and Gynecology, Oakwood Hospital and Medical Center, Dearborn, Michigan, USA.
Obstet Gynecol. 1997 May;89(5 Pt 1):734-7. doi: 10.1016/s0029-7844(97)00089-6.
To evaluate the fetal iliac wing angle in detecting trisomy 21 in the second trimester of pregnancy.
Using an axial view of the fetal pelvis, the angle between the right and left iliac wings (iliac wing angle) was measured ultrasonographically at the time of the second-trimester ultrasound or genetic amniocentesis in 377 singleton fetuses. Trisomy 21 was diagnosed by karyotype results from the amniocentesis or newborn examination with karyotype if trisomy 21 was suspected based on phenotypic features. Sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) were calculated using multiple cutoff points. A receiver operating characteristic (ROC) curve was used to identify the optimum iliac wing angle. Descriptive statistics and Student t test were utilized for analyses with a P of less than .05 considered significant.
The average gestational age was 18.8 weeks (range 13-32). Karyotypes were available in 128 fetuses. The overall prevalence of trisomy 21 was 11 of 377 (2.9%). The mean (+/-standard deviation) iliac wing angle in the normal fetuses was 68.2 degrees (+/-15.4 degrees) and 98.5 degrees (+/-11.3 degrees) in fetuses with trisomy 21 (P < .001). Using an ROC-derived absolute cutoff of 90 degrees, an abnormal iliac wing angle had sensitivity of 90.9% (ten of 11), specificity of 94.5% (346 of 366), NPV of 99.7% (346 of 347), and PPV of 33.3% (ten of 30) to detect trisomy 21.
Fetuses with trisomy 21 have greater iliac wing angles than do normal fetuses. Using an ROC-derived absolute cutoff of 90 degrees, we could detect 90.9% of fetuses with trisomy 21 with a PPV of 33% in our high-risk population. These findings suggest that iliac wing angle is a useful marker in antenatal screening for trisomy 21.
评估孕中期胎儿髂骨翼角度在检测21三体综合征中的作用。
在377名单胎胎儿的孕中期超声检查或遗传羊膜穿刺术时，利用胎儿骨盆的轴位视图，超声测量左右髂骨翼之间的角度（髂骨翼角度）。如果根据表型特征怀疑为21三体综合征，则通过羊膜穿刺术的核型结果或新生儿核型检查来诊断21三体综合征。使用多个截断点计算敏感性、特异性、阳性预测值（PPV）和阴性预测值（NPV）。采用受试者工作特征（ROC）曲线确定最佳髂骨翼角度。采用描述性统计和Student t检验进行分析，P值小于0.05认为具有统计学意义。
平均孕周为18.8周（范围13 - 32周）。128例胎儿有核型结果。21三体综合征的总体患病率为377例中的11例（2.9%）。正常胎儿的平均（±标准差）髂骨翼角度为68.2度（±15.4度），21三体综合征胎儿为98.5度（±11.3度）（P < 0.001）。使用ROC得出的绝对截断值90度，异常髂骨翼角度检测21三体综合征的敏感性为90.9%（11例中的10例），特异性为94.5%（366例中的346例），NPV为99.7%（347例中的346例），PPV为33.3%（30例中的10例）。
21三体综合征胎儿的髂骨翼角度大于正常胎儿。在我们的高危人群中，使用ROC得出的绝对截断值90度，我们可以检测出90.9%的21三体综合征胎儿，PPV为33%。这些发现表明髂骨翼角度是产前筛查21三体综合征的一个有用标志物。
