Risk Stratification for Congenital Heart Surgery for ICD-10 Administrative Data (RACHS-2)

Background: As the cardiac community strives to improve outcomes, accurate methods of risk adjustment are imperative. Since adoption of International Disease Classification-10 (ICD-10) in 2015, there is no published method for congenital heart surgery risk stratification for administrative data. Objectives: Our objective was to develop an empirically derived, publicly available, Risk Stratification for Congenital Heart Surgery (RACHS-2) tool for ICD-10 administrative data. Methods: The RACHS-2 stratification system was iteratively and empirically refined in a training dataset of Pediatric Health Information Systems claims to optimize sensitivity and specificity when compared to corresponding, locally-held Society of Thoracic Surgeons-Congenital Heart Surgery (STS-CHS) clinical registry data. The tool was validated in a second administrative data source, New York State Medicaid claims. Logistic regression was used to compare the ability of RACHS-2 in administrative data to predict operative mortality vs. STAT Mortality Categories in registry data. Results: The RACHS-2 system captured 99.6% of total congenital heart surgery registry cases, with 1.0% false positives. RACHS-2 predicted operative mortality in both training and validation administrative datasets similarly to STAT Mortality Categories in registry data. C-statistics for models for operative mortality in training and validation administrative datasets—adjusted for RACHS-2—were 0.76 and 0.84 (95% CIs 0.72-0.80 and 0.80-0.89); C-statistics for models for operative mortality—adjusted for STAT Mortality Categories—in corresponding clinical registry data were 0.75 and 0.84 (95% CIs 0.71-0.79 and 0.79-0.89). Conclusions: RACHS-2 is a risk stratification system for pediatric cardiac surgery for ICD-10 administrative data, validated in two administrative/registry linked datasets. Statistical code is publicly available upon request.