Predictive Performance for Hospital Mortality of SAPS 3, SOFA, ISS, and New ISS in Critically Ill Trauma Patients: A Validation Cohort Study

Abstract

Background: It is not known whether anatomical scores perform better than general critical care scores for trauma patients admitted to the intensive care unit (ICU). We compare the predictive performance for hospital mortality of general critical care scores (SAPS 3 and SOFA) with anatomical injury-based scores (Injury Severity Score [ISS] and New ISS [NISS]). Methods: Retrospective cohort study of patients admitted to a specialized trauma ICU from a tertiary hospital in São Paulo, Brazil between May, 2012 and January, 2016. We retrieved data from the ICU database for critical care scores and calculated ISS and NISS from chart data and whole body computed tomography results. We compared the predictive performance for hospital mortality of each model through discrimination, calibration, and decision-curve analysis. Results: The sample comprised 1053 victims of trauma admitted to the ICU, with 84.2% male patients and mean age of 40 (±18) years. Main injury mechanism was blunt trauma (90.7%). Traumatic brain injury was present in 67.8% of patients; 43.3% with severe TBI. At the time of ICU admission, 846 patients (80.3%) were on mechanical ventilation and 644 (64.3%) on vasoactive drugs. Hospital mortality was 23.8% (251). Median SAPS 3 was 41; median maximum SOFA within 24 h of admission, 7; ISS, 29; and NISS, 41. AUROCs (95% CI) were: SAPS 3 = 0.786 (0.756-0.817), SOFA = 0.807 (0.778-0.837), ISS = 0.616 (0.577-0.656), and NISS = 0.689 (0.649-0.729). In pairwise comparisons, SAPS 3 and SOFA did not differ, while both outperformed the anatomical scores ( p < .001). Maximum SOFA within 24 h of admission presented the best calibration and net benefit in decision-curve analysis. Conclusions: Trauma-specific anatomical scores have fair performance in critically ill trauma patients and are outperformed by SAPS 3 and SOFA. Illness severity is best characterized by organ dysfunction and physiological variables than anatomical injuries.