Comparison between an empirically derived model and the EuroSCORE system in the evaluation of hospital performance: the example of the Italian CABG Outcome Project

Objectives: To compare the risk-adjustment model empirically derived from the ‘Italian CABG Outcome Project’ with that of the additive and logistic EuroSCORE in terms of accuracy, predictive power and ability to rank hospital performances. Methods: The Italian CABG model, the logistic and additive EuroSCORE were applied to the Italian CABG population; the observed deaths/expected deaths (O/E) ratios, as obtained by the three models, were computed for each Italian cardiac surgery centre and for six classes of risk-stratified patients. The performance of the three models in predicting the 30-day mortality was formally assessed for calibration (Hosmer–Lemeshow test) and discrimination (ROC area). According to the three models, risk-adjusted mortality rates (RAMR = O/E × Italian CABG population mortality rate) were estimated for each centre; possible differences were detected in the identification of hospitals with mortality rates higher and lower than average. Results: The Italian CABG model uses fewer variables than the EuroSCORE system (14 vs 17) and exhibits the best performance in terms of discrimination and calibration. Contrary to the other tested models, the logistic EuroSCORE shows a significant Hosmer–Lemeshow test ( , p