Performance of the early warning system score in predicting postoperative complications in older versus younger patients

Abstract

BACKGROUND: Early warning system (EWS) scores are implemented on surgical wards to identify patients at high risk of postoperative clinical deterioration, but its predictive value in older patients is unclear. This study assessed the prognostic value of EWS scores to predict severe postoperative complications in older patients compared to younger patients. METHODS: This study utilized data from the TRACE study. EWS scores were routinely measured on postoperative days one (POD1) and three (POD3). The cohort was divided by age: < 70 years and ≥ 70 years. Performance measures of EWS scores on POD1 and POD3 were assessed to predict severe postoperative complications. Missed event rates (proportion of events not detected by the EWS threshold) and nonevent rates (proportion of EWS values above the threshold without an adverse event) were calculated. RESULTS: Among 4866 patients, 39.3% were ≥ 70 years old. Severe complications occurred in 6.1% of older compared to 5.8% of younger patients (P = 0.658). EWS scores on POD1 and POD3 did not differ between age groups. For severe complications, EWS showed moderate discrimination in both older (POD1: C-statistic 0.65 (95%CI 0.59-0.70); POD3: 0.63 (95%CI 0.57-0.69)) and younger patients (POD1: 0.68 (95%CI 0.65-0.72); POD3: 0.65 (95%CI 0.61-0.70)). Overall, calibration was good. For EWS score ≥ 3, the missed event rate was at least 69% and nonevent rate 75%. CONCLUSIONS: Predicted performance of the EWS score was moderate among older and younger patients. A limitation of the EWS score is the high rate of missed events and nonevents.