Does EuroSCORE II perform better than its original versions? A multicentre validation study

The European System for Cardiac Operation Risk Evaluation (EuroSCORE) is widely used for predicting in-hospital mortality after cardiac surgery. A new score (EuroSCORE II) has been recently developed to update the previously released versions. This study was undertaken to validate EuroSCORE II, to compare its performance with the original EuroSCOREs and to evaluate the effects of the removal of those factors that were included in the score even if they were statistically non-significant. Data on 12 325 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 comparison among the scores performances was performed with Delong, bootstrap, and Venkatraman methods. Calibration was evaluated with calibration curves and associated statistics. The in-hospital mortality rate was 2.2. The discriminatory power was high and similar in all algorithms (area under the curve 0.82, 95 CI: 0.790.84 for additive EuroSCORE; 0.82, 95 CI: 0.790.84 for logistic EuroSCORE; 0.82, 95 CI: 0.800.85 for EuroSCORE II). The EuroSCORE II had a fair calibration till 30-predicted values and over-predicted beyond. The removal of non-significant factors from EuroSCORE II did not affect performance, being both the calibration and discrimination comparable. This validation study demonstrated that EuroSCORE II is a good predictor of perioperative mortality. It showed an optimal calibration until 30-predicted mortality. Nonetheless, it does not seem to significantly improve the performance of older versions in the higher tertiles of risk. Moreover, it could be simplified, as the removal from the algorithm of non-significant factors does not alter its performance.