Performance of Society of Thoracic Surgeons and EuroSCORE II pre-surgical mortality risk score for cardiac surgery in a large majority-minority population

Abstract

Abstract Background Pre-surgical mortality risk scores are important tools for pre-operative assessment. The Society of Thoracic Surgeons (STS) and EuroSCORE II (ES) scores were derived from predominantly white populations; their utility in minority populations is understudied. Purpose To compare the performance of STS and ES in a large majority-majority population. Methods We used cardiac surgery registry data from a tertiary care, 500-bed, university-affiliated hospital. For each patient, STS and ES risk of mortality were calculated. We measured model performance by discrimination (ROC-AUC) and calibration (O/E ratios). We compared performance by racial subgroups, and explored differences in risk stratification by race and risk category by measuring risk reclassification if ES were used instead of STS. Results From 2009–20, 4061 patients underwent CABG (68%), valve (18%), or CABG/valve (7%) surgery. Of these, 51% were Asian (n=2076), 24% Native Hawaiian and other Pacific Islander (NHPI) (n=977), 23% White (n=919) and 3% Other (n=79). Overall, STS underestimated (O/E: 1.09) and ES overestimated (O/E: 0.55) mortality risk. STS had better discrimination (ROC-AUC: 0.83 vs 0.77). STS model calibration was better among Asians (O/E: 1.03) than NHPI (O/E: 1.22) and Whites (O/E: 1.14). ES calibration was poor overall (Asian O/E: 0.58, NHPI O/E: 0.54, White O/E: 0.50). Discrimination was similar in STS (Asian AUC: 0.83, NHPI AUC: 0.85, White AUC: 0.86) and ES (Asian AUC: 0.77, NHPI AUC: 0.77, White AUC: 0.81), although it did perform better for White patients. Of patients defined as Low Risk by STS, 31% were reclassified as Intermediate or High Risk by ES. Of patients defined as High Risk by STS, 27% were downgraded to Intermediate or Low Risk by ES. This differed by race. For Asians, 28% at Low Risk and 31% at High Risk by STS were reclassified when using ES. For NHPI, 36% at Low Risk and 22% of High Risk by STS were reclassified by ES. For Whites, 31% at Low Risk and 19% of High Risk by STS were reclassified by ES. Conclusion The choice of pre-surgical risk score can impact estimates of pre-cardiac surgery risk of mortality. While STS performs better than ES in our majority minority population, there are significant differences by race. Funding Acknowledgement Type of funding sources: None.