Study of Z-score of fetal heart circumference and heart area in prediction of homozygous α-thalassemia / 中华超声影像学杂志

ABSTRACT

Objective:To explore the values of Z-scores of fetal heart circumference (HC) and heart area (HA) in prediction of homozygous α-thalassemia.Methods:From February 2014 to March 2019, 233 fetuses of 15 to 23 gestation weeks with risk of homozygous α-thalassemia were examined by prenatal ultrasound in the Maternal and Child Health Hospital of Guangxi Zhuang Autonomous Region. HC, HA and cardiothoracic ratio (CTR) were measured. HC and HA were converted into Z-scores, respectively. The ROC curves were established and analyzed based on HC Z-score, HA Z-score or CTR respectively to compare their predicting efficacies for fetal homozygous α-thalassemia. Finally, the sensitivity, specificity, positive predictive value and negative predictive value were obtained by the best cutoff values.Results:①Sixty-five fetuses were diagnosed as homozygous α-thalassemia and classified as α-thalassemia group. One hundred and sixty-eight fetuses were mild and normal and were classified as control group. ②HC Z-score, HA Z-score and CTR in the α-thalassemia group were significantly higher than those in the control group, and the differences between the two groups were statistically significant ( P<0.001). ③The area under ROC curve of HA Z-score was the largest compared with HC Z-score and CTR, and the prediction efficacy was the highest ( Z test=2.144 and 2.517 respectively, P<0.05). ④The best cutoff values were HC Z-score>1.67, HA Z-score>2.06 and CTR>0.53. Sensitivities of predicting homozygous α-thalassemia in 15 to 23 gestation weeks were 92.31%, 100% and 89.23%, respectively. Specificities were 94.05%, 95.83% and 93.45%, respectively. Positive predictive values were 84.43%, 89.00% and 84.05%, respectively. Negative predictive values were 96.91%, 100% and 95.57%, respectively. Conclusions:Fetal heart HC Z-score and HA Z-score are safe and effective novel ultrasonic indexes for predicting homozygous α-thalassemia. Especially compared with traditional CTR, HA Z-score has a significantly higher predicting efficacy, which can improve the detection rate of homozygous α-thalassemia and reduce the need for invasive examination.