RÉSUMÉ
OBJECTIVE: To examine the external validity of a well-known congenital diaphragmatic hernia (CDH) clinical prediction model using a population-based cohort. STUDY DESIGN: Newborns with CDH born in California between 2007 and 2012 were extracted from the Vital Statistics and Patient Discharge Data Linked Files. The total CDH risk score was calculated according to the Congenital Diaphragmatic Hernia Study Group (CDHSG) model using 5 independent predictors: birth weight, 5-minute Apgar, pulmonary hypertension, major cardiac defects, and chromosomal anomalies. CDHSG model performance on our cohort was validated for discrimination and calibration. RESULTS: A total of 705 newborns with CDH were extracted from 3 213 822 live births. Newborns with CDH were delivered in 150 different hospitals, whereas only 28 hospitals performed CDH repairs (1-85 repairs per hospital). The observed mortality for low-, intermediate-, and high-risk groups were 7.7%, 34.3%, and 54.7%, and predicted mortality for these groups were 4.0%, 23.2%, and 58.5%. The CDHSG model performed well within our cohort with a c-statistic of 0.741 and good calibration. CONCLUSIONS: We successfully validated the CDHSG prediction model using an external population-based cohort of newborns with CDH in California. This cohort may be used to investigate hospital volume-outcome relationships and guide policy development.