Applicability of the Commonly Used Risk Scores for Coronary Bypass Surgery in Algeria

Objectives: 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) as well as the initial logistic Parsonnet risk score, who have been developed from European and American datasets, is questionable outside these regions. We aimed to assess the performance of these three risk scores for patients undergoing isolated coronary artery bypass grafting (CABG) in Algeria.

Methods: Between June 2014 and June 2016, data from 235 consecutive patients, who underwent isolated CABG at a reference center in Algiers, were prospectively collected and scored according to the EuroSCORE II, STS-PROM and the Parsonnet score. Their discriminative power was evaluated by the area under the receiver operating characteristic curve (AUC) while their calibration was 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, STS-PROM and by Parsonnet risk score was: 1.33%, 0.78% and 3.35%, respectively. Discriminatory ability was fair for the Parsonnet risk score, good for the STS PROM and excellent for EuroSCORE II (AUCs = 0.737, 0.788, and 0.892, respectively). Regarding calibration, EuroSCORE II and STS-PROM under estimated observed mortality (Hosmer-Lemeshow test: P< 0.001 for both scores), while the Parsonnet risk score was well calibrated (Hosmer-Lemeshow test: p = 0.395).

Conclusions: EuroSCORE II and STS-PROM had excellent and good discriminating power, respectively, but both underestimated the risk of 30 days mortality following isolated CABG at a reference center in Algiers. The Parsonnet risk score was well calibrated but was moderately discriminating. The development of a local risk score or the recalibration of recent international risk scores is necessary.