Objectives: The purpose of this study was to evaluate the impact of standardization of the lung-to-head ratio measurements in isolated congenital diaphragmatic hernia on prediction of neonatal outcomes and reproducibility.
Methods: We conducted a retrospective cohort study of 77 cases of isolated congenital diaphragmatic hernia managed in a single center between 2004 and 2012. We compared lung-to-head ratio measurements that were performed prospectively in our institution without standardization to standardized measurements performed according to a defined protocol.
Results: The standardized lung-to-head ratio measurements were statistically more accurate than the nonstandardized measurements for predicting neonatal mortality (area under the receiver operating characteristic curve, 0.85 versus 0.732; P = .003). After standardization, there were no statistical differences in accuracy between measurements regardless of whether we considered observed-to-expected values (P > .05). Standardization of the lung-to-head ratio did not improve prediction of the need for extracorporeal membrane oxygenation (P> .05). Both intraoperator and interoperator reproducibility were good for the standardized lung-to-head ratio (intraclass correlation coefficient, 0.98 [95% confidence interval, 0.97-0.99]; bias, 0.02 [limits of agreement, -0.11 to +0.15], respectively).
Conclusions: Standardization of lung-to-head ratio measurements improves prediction of neonatal outcomes. Further studies are needed to confirm these results and to assess the utility of standardization of other prognostic parameters.
Keywords: congenital diaphragmatic hernia; fetal lung; lung-to-head ratio; obstetric ultrasound; pulmonary hypoplasia; standardization.