Predicting Survival after Trauma: a Comparison of TRISS and ASCOT in the Netherlands

Abstract

Background: Evaluating the performance of a trauma system may be attempted by comparing outcome in different trauma populations. Controlling for injury severity is a necessity for such evaluations. We compare two current models for doing so: the “Trauma and Injury Severity Score” (TRISS) and “A Severity Characterization Of Trauma” (ASCOT). Material and Methods: This study of high-energy trauma victims took place in Leiden, the Netherlands, between 1993 and 1998. Using the Hosmer-Lemeshow (HL) test and receiver operator characteristic (ROC) analysis, the TRISS and ASCOT models were compared for calibration and discrimination. Results: 1,024 patients, with an average Injury Severity Score (ISS) of 13.5, were eligible for inclusion. Blunt trauma was the predominant cause of injuries. Both models gave accurate, though pessimistic, results in predicting the actual number of fatalities (n = 71). The HL test indicated a sufficient fit for the ASCOT model (p = 0.28) and an insufficient fit (p = 0.02) for TRISS. The ROC curves were nearly identical (0.97). Including age as a linear variable, instead of using the current age groups, resulted in an improved discriminative power of the models. Conclusions: The ASCOT model proved superior over TRISS in its accuracy to estimate of survival chances. This difference was most evident for victims with an estimated survival chance of 60–90%. Future national trauma researchers should therefore collect ASCOT data. Improved ASCOT models could be developed, with age as a linear variable.