Reproducibility of lung-to-head ratio ultrasound measurements in congenital diaphragmatic hernia

Objectives—This study investigated the reproducibility of standardization of lungto- head ratio measurements in congenital diaphragmatic hernia (CDH) at our center among sonographers after we standardized the method. Methods—We reviewed ultrasound images of 12 fetuses with CDH at Mayo Clinic from 2010 to 2016. Nine operators (1 maternal-fetal medicine specialist with experience in measuring the lung-to-head ratio and 8 sonographers), who were blinded to previous findings, reviewed 33 selected images from 12 fetuses with left CDH. The method for lung-to-head ratio measurement was standardized before starting the measurements. The lung-to-head ratio was assessed by different methods to obtain the lung areas: anteroposterior, longest, and area tracing. We evaluated the correlation between operators using the intraclass correlation coefficient (ICC). We also compared agreement between the sonographers and a physician with experience in measuring the lung-to-head ratio using a Bland-Altman analysis. Results—The methods with the best interoperator reproducibility were the standardized anteroposterior lung-to-head ratio (ICC, 0.69) and the standardized lung-to-head ratio tracing (ICC, 0.65) compared to the longest lung-to-head ratio (ICC, 0.56). The standardized lung-to-head ratio tracing had the best agreement among sonographers and the physician (bias, 0.11; limits of agreement, 20.27 to10.49) than the anteroposterior lung-to-head ratio (bias, 0.35; limits of agreement, 20.13 to10.83) and the longest lung-to-head ratio (bias, 0.27; limits of agreement,20.35 to10.89). Conclusions—We demonstrated that the lung-to-head ratio tracing method has high interoperator reproducibility and the best agreement among the operators at our center. Further multicenter studies are necessary to confirm our results.