External validation of the EuroSCORE II and the STSPROM for patients undergoing isolated coronary artery bypass grafting in a developing country

Abstract Introduction The applicability of European system for cardiac operative risk evaluation II (EuroSCORE II) and the Society of Thoracic Surgeons Predicted Risk of Mortality (STS-PROM), which have been developed mostly from European and American datasets, is questionable outside these regions. Purpose We aimed to assess the performance of these two risk scores for patients undergoing isolated coronary artery bypass grafting (CABG) in a developing country. Methods Data from 235 consecutive patients, who underwent isolated CABG, were prospectively collected and scored according to the EuroSCORE II and STS-PROM. The discriminative powers of these risk scores were evaluated by the area under the receiver operating characteristic curve (AUC) and were compared by the De Long's test, while their calibrations were tested by the Hosmer-Lemeshow goodness-of-fit test. Results The mean patient age was 59.08 years and 18.3% were female. The mortality at 30 days was 3.40%. The mortality expected by EuroSCORE II and by STS-PROM was: 1.33% and 0.78%, respectively. Discriminatory ability was good for the STS PROM and excellent for EuroSCORE II (AUCs = 0.788, and 0.892, respectively) (Figure 1). The comparison between their AUCs showed that the EuroSCORE II outperformed significantly the STS-PROM (0.893 versus 0.788. 95% Confidence Interval: 0.004-0.204, P = 0.041). Regarding calibration, EuroSCORE II and STS-PROM under estimated observed mortality (Hosmer-Lemeshow test: P˂ 0.001 for both scores) ( Figure 2). Conclusion EuroSCORE II and STS-PROM had excellent and good discriminating power, respectively, but both underestimated the risk of 30 days mortality following isolated CABG in a developing country. The development of a local risk score or the recalibration of EuroSCORE II or STSPROM is necessary outside the countries where they were originally developed.ROC curves for isolated CABG Calibration plots for isolated CABG