Introduction: Previous research showed that there is no agreement on a practically applicable model to use in the evaluation of trauma care. A modification of the Trauma and Injury Severity Score (modified TRISS) is used to evaluate trauma care in the Netherlands. The aim of this study was to evaluate the prognostic ability of the modified TRISS and to determine where this model needs improvement for better survival predictions. Methods: Patients were included if they were registered in the Brabant Trauma Registry from 2010 through 2015. Missing values were imputed according to multiple imputation. Subsets were created based on age, length of stay, type of injury and injury severity. Probability of survival was calculated with the modified TRISS. Discrimination was assessed with the Area Under the Receiver Operating Curve (AUROC). Calibration was studied graphically. Results: The AUROC was 0.84 (95% CI: 0.83, 0.85) for the total cohort (N = 69 747) but only 0.53 (95% CI: 0.51, 0.56) for elderly patients with hip fracture. Overall, calibration of the modified TRISS was adequate for the total cohort, with an overestimation for elderly patients and an underestimation for patients without brain injury. Conclusions: Outcome comparison conducted with TRISS-based predictions should be interpreted with care. If possible, future research should develop a simple prediction model that has accurate survival prediction in the aging overall trauma population (preferable with patients with hip fracture), with readily available predictors.

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Keywords Performance, Prediction model, Subpopulations, Trauma, TRISS
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Journal Injury: International Journal of the Care of the Injured
de Munter, L. (Leonie), Polinder, S, Nieboer, D, Lansink, K.W.W, Steyerberg, E.W, & de Jongh, M.A.C. (2018). Performance of the modified TRISS for evaluating trauma care in subpopulations: A cohort study. Injury: International Journal of the Care of the Injured. doi:10.1016/j.injury.2018.03.036