Evaluation of the EuroSCORE risk scoring model for patients undergoing coronary artery bypass graft surgery: a word of caution.

Abstract

Background. Risk-adjusted mortality rates are used to compare quality of care of different hospitals. We evaluated the EuroSCORE (European System for Cardiac Operative Risk Evaluation) in patients undergoing isolated coronary artery bypass grafting (CABG).Patients and method. Data of all CABG patients from January 2004 until December 2008 were analysed. Receiver-operating characteristics (ROC) curves for the additive and logistic EuroSCOREs and the areas under the ROC curve were calculated. Predicted probability of hospital mortality was calculated using logistic regression analyses and compared with the EuroSCORE. Cumulative sum (CUSUM) analyses were performed for the EuroSCORE and the actual hospital mortality.Results. 5249 patients underwent CABG of which 89 (1.7%) died. The mean additive EuroSCORE was 3.5+/-2.5 (0-17) (median 3.0) and the mean logistic EuroSCORE was 4.0+/-5.5 (0-73) (median 2.4). The area under the ROC curve was 0.80+/-0.02 (95% confidence interval (CI) 0.76 to 0.84) for the additive and 0.81+/-0.02 (0.77 to 0.85) for the logistic EuroSCORE. The predicted probability (hazard ratio) was different from the additive and logistic EuroSCOREs. The hospital mortality was half of the EuroSCOREs, resulting in positive variable life-adjusted display curves. Conclusions. Both the additive and logistic EuroSCOREs are overestimating the in-hospital mortality risk in low-risk CABG patients. The logistic EuroSCORE is more accurate in high-risk patients compared with the additive EuroSCORE. Until a more accurate risk scoring system is available, we suggest being careful when comparing the quality of care of different centres based on risk-adjusted mortality rates. (Neth Heart J 2010;18:355-9.).