Value of the ratio of fetal cardiac diameter to biparietal diameter in prediction of homozygous α-thalassemia-1 fetuses

Abstract

Objective To evaluate the efficacy of the ratio of the fetal cardiac diameter to biparietal diameter(CBR) as a predictor of homozygous α-thalassemia-1. Methods Single mid-pregnancies(15-22weeks) at risk of homozygous α-thalassemia-1 were enrolled. A total of 251 singleton pregnancies were recruited, in which 63 cases were homozygous α-thalassemia-1 fetuses and the rest were unaffected. The CBR and cardiothoracic ratio(CTR) were measured by two-dimensional ultrasound. Then the accuracy of these variables were analyzed and compared with each other by ROC curves. Results ①The CBR and CTR in affected fetuses were significantly higher than those in the unaffected(P 0.43 and CTR>0.52 as the best cut off values, the sensitivity and specificity of predicting homozygous α-thalassemia-1 fetuses in 15-22 gestational weeks were 95.74%, 92.06% and 94.15%, 85.71%, respectively; the area under ROC curve were compared with Z test and there was no significant difference between them (Z=1.500, P=0.1335). ③When CBR and CTR were combined, the sensitivity and specificity of the prediction were significantly increased (the sensitivity of series experiment: 99.75%, the specificity of parallel experiment: 98.87%). Conclusions CBR is a novel, effective and noninvasive predictor of homozygous α-thalassemia-1 in mid-pregnancy whose prediction efficiency is the same as traditional CTR. The measurement of CBR is easier to standardize and is not affected by thoracic lesions such as pleural cavity, pericardial effusion and skeletal dysplasia. If combined with CTR, it may play an important role in improving the prenatal detection rate of homozygous α-thalassemia-1 fetuses. Key words: Echocardiography; Prenatal diagnosis; Alpha-thalassemia; Cardiac diameter to biparietal diameter ratio; Cardiothoracic ratio