External validation of European System for Cardiac Operative Risk Evaluation II in a Tunisian population

Objective: The main objective of this study is to evaluate the performance of the predictive model (EuroSCORE II) on a Tunisian population in order to validate its use in our country. Methods: This is a retrospective study of data from 418 adult patients undergoing cardiac surgery with cardiopulmonary bypass between 1st January 2015 and 31 December 2016 in the department of cardiovascular and thoracic surgery of the Sahloul University Hospital of Sousse. The EuroSCORE ΙΙ is calculated using the application validated on the site www.euroscore.org. The performance of the score is evaluated by analyzing its discriminative power by constructing the ROC curve and analyzing its calibration using the Hosmer-Lemeshow statistics. Results: The EuroSCORE II shows good discriminative power in our population with an area under the ROC curve >0.7 in all study groups (0.864 ± 0.032 for general cardiac surgery, 0.822 ± 0.061 for coronary surgery, 0.864 ± 0.052 for valvular surgery, and 0.900 ± 0.041 for urgent cardiac surgery). The model appears to be calibrated as well by obtaining ρ values above the statistical significance level of 0.05 (0.638 for general cardiac surgery, 0.543 for coronary surgery, 0.179 for valvular surgery, and 0.082 for urgent cardiac surgery). Conclusion: The EuroSCORE II presents acceptable performance in our population, attested by a good discriminative power and an adequate calibration.