In-hospital mortality risk assessment in elective and non-elective cardiac surgery : a comparison between EuroSCORE II and age, creatinine, ejection fraction (ACEF) score

OBJECTIVES: Age, creatinine, ejection fraction (ACEF) score is a simplified algorithm for prediction of mortality after elective cardiac surgery. Although mainly conceived for elective cardiac surgery, no information is available on its performance in non-elective surgery and on comparison with the new EuroSCORE II. This study was undertaken to compare the performance of ACEF score and EuroSCORE II within classes of urgency. METHODS: Complete data on 13 871 consecutive patients who underwent major cardiac surgery in a 6-year period were retrieved from three prospective institutional databases. Discriminatory power was assessed using the c-index and h with Delong, bootstrap and Venkatraman methods. Calibration was evaluated with calibration curves and associated statistics. RESULTS: The in-hospital mortality rate was 2.5%. The discriminatory power of ACEF score within elective and non-elective surgery was similar (area under the curve (AUC) 0.71, 95% confidence interval (CI) 0.67-0.74 and AUC 0.68, 95% CI 0.62-0.73, respectively) but significantly lower than that of EuroSCORE II (AUC 0.80, 95% CI 0.77-0.83 for elective surgery; AUC 0.82, 95% CI 0.78-0.85 for non-elective surgery). The calibration patterns were different in the two subgroups, but the summary statistics underscored a miscalibration in both of them (U-statistic and Spiegelhalter Z-test P-values <0.05). Even the calibration of EuroSCORE II was insufficient, although it was demonstrated to be well calibrated in the first tertile of predicted risk. CONCLUSIONS: This study demonstrated that the performance of ACEF score in predicting in-hospital mortality in elective and non-elective cardiac surgery is comparable. Nonetheless, it is not as satisfactory as the new EuroSCORE II, as its discrimination is significantly lower and it is also miscalibrated. KEYWORDS: Epidemiology, Outcomes research, Risk factors, Risk score, Surgery