Comparison of the EuroSCORE and Cardiac Anesthesia Risk Evaluation (CARE) score for risk-adjusted mortality analysis in cardiac surgery

OBJECTIVE: The European System for Cardiac Operative Risk Evaluation (EuroSCORE) and the Cardiac Anesthesia Risk Evaluation (CARE) score are risk indices designed in the mid-1990 s to predict mortality after cardiac surgery. This study assesses their ability to provide risk-adjusted mortality in a contemporary cardiac surgical population. METHODS: The mortality probability was estimated with the additive and logistic EuroSCORE, and CARE score, for 3818 patients undergoing cardiac surgery at one institution between 1 April 2006 and 31 March 2009. Model discrimination was obtained using the area under the receiver operating characteristics (ROC) curve and calibration using the appropriate chi-square goodness-of-fit test. Recalibration of risk models was obtained by logistic calibration, when needed. Calculation of risk-adjusted mortality was performed for the institution and eight surgeons, using each model before and when needed, after recalibration. RESULTS: The area under the ROC curve is 0.72 (95% confidence interval (CI): 0.71-0.74) with the additive EuroSCORE, 0.84 (95% CI: 0.83-0.85) with the logistic EuroSCORE, and 0.79 (95% CI: 0.78-0.81) with the CARE score. The additive and logistic EuroSCORE have poor calibration, predicting a hospital mortality of 6.24% and 7.72%, respectively, versus an observed mortality of 3.25% (P < 0.001). Consequently, the risk-adjusted mortality obtained with those models is significantly underestimated for the institution and all surgeons. The CARE score has good calibration, predicting a mortality of 3.38% (P = 0.50). The hospital risk-adjusted mortality with the recalibrated additive and logistic EuroSCORE and CARE score is 3.24% (95% CI: 3.05-3.43%), 3.25% (95% CI: 3.05-3.44%), and 3.12% (95% CI: 2.94-3.34%), respectively. The individual surgeons' risk-adjusted mortality is similar with the recalibrated EuroSCORE models and CARE score, identifying two surgeons with higher rates than the hospital average mortality. CONCLUSIONS: The original additive and logistic EuroSCORE models significantly overestimate the risk of mortality after cardiac surgery. However, after recalibration both models provide reliable risk-adjusted mortality results. Despite its lower discrimination as compared with the logistic EuroSCORE, the CARE score remains calibrated a decade after its development. It is as robust as the recalibrated additive and logistic EuroSCORE to perform risk-adjusted mortality analysis.