Comparison of mortality prediction models and validation of SAPS II in critically ill burns patients

Specific burn outcome prediction scores such as the Abbreviated Burn Severity Index (ABSI), Ryan, Belgian Outcome of Burn Injury (BOBI) and revised Baux scores have been extensively studied. Validation studies of the critical care score SAPS II (Simplified Acute Physiology Score) have included burns patients but not addressed them as a cohort. The study aimed at comparing their performance in a Swiss burns intensive care unit (ICU) and to observe whether they were affected by a standardized definition of inhalation injury. We conducted a retrospective cohort study, including all consecutive ICU burn admissions (n=492) between 1996 and 2013: 5 epochs were defined by protocol changes. As required for SAPS II calculation, stays <24h were excluded. Data were collected on age, gender, total body surface area burned (TBSA) and inhalation injury (systematic standardized diagnosis since 2006). Study epochs were compared (χ2 test, ANOVA). Score performance was assessed by receiver operating characteristic curve analysis. SAPS II performed well (AUC 0.89), particularly in burns <40% TBSA (AUC 0.93). Revised Baux and ABSI scores were not affected by the standardized diagnosis of inhalation injury and showed the best performance (AUC 0.92 and 0.91 respectively). In contrast, the accuracy of the BOBI and Ryan scores was lower (AUC 0.84 and 0.81) and reduced after 2006. The excellent predictive performance of the classic scores (revised Baux score and ABSI) was confirmed. SAPS II was nearly as accurate, particularly in burns <40% TBSA. Ryan and BOBI scores were least accurate, as they heavily weight inhalation injury.