Summary Background Data: The trauma injury severity score (TRISS) has been used for over 20 years for retrospective risk assessment in trauma populations. The TRISS has serious limitations, which may compromise the validity of trauma care evaluations.
Objective: To derive and validate a new mortality prediction model, the trauma risk adjustment model (TRAM), and to compare the performance of the TRAM to that of the TRISS in terms of predictive validity and risk adjustment.
Methods: The Quebec Trauma Registry (1998–2005), based on the mandatory participation of 59 designated provincial trauma centers, was used to derive the model. The American National Trauma Data Bank (2000–2005), based on the voluntary participation of any US hospitals treating trauma, was used for the validation phase. Adult patients with blunt trauma respecting at least one of the following criteria were included: hospital stay >2 days, intensive care unit admission, death, or hospital transfer. Hospital mortality was modeled with logistic generalized additive models using cubic smoothing splines to accommodate nonlinear relations to mortality. Predictive validity was assessed with model discrimination and calibration. Risk adjustment was assessed using comparisons of risk-adjusted mortality between hospitals.
Results: The TRAM generated an area under the receiving operator curve of 0.944 and a Hosmer-Lemeshow statistic of 42 in the derivation phase. In the validation phase, the TRAM demonstrated better model discrimination and calibration than the TRISS (area under the receiving operator curve = 0.942 and 0.928, P < 0.001; Hosmer-Lemeshow statistics = 127 and 256, respectively). Replacing the TRISS with the TRAM led to a mean change of 28% in hospital risk-adjusted odds ratios of mortality.
Conclusions: Our results suggest that adopting the TRAM could improve the validity of trauma care evaluations and trauma outcome research.
The trauma and injury severity score has been used for over 2 decades for risk adjustment in trauma care assessment despite its documented limitations. The present study introduces the trauma risk adjustment model, which addresses the major limitations of the trauma and injury severity score and demonstrates significantly better predictive validity. Replacing the trauma and injury severity score with the trauma risk adjustment model has a measurable influence on the results of trauma centre mortality comparisons.
From the *Unité de traumatologie-urgence-soins intensifs, Centre de recherche du CHA (Hôpital de l'Enfant-Jésus), Quebec City, Quebec, Canada; †Département de médecine sociale et préventive, Université Laval, Quebec City, Quebec, Canada; ‡Département d’anesthésiologie, division de soins intensiks, Hôpital de l’Enfant-Jésus, Université Laval, Quebec City, Quebec, Canada; §Département de médecine familiale, Université Laval, Quebec City, Quebec, Canada; ¶Department of Surgery, McGill University Health Center, McGill University, Montreal, Quebec, Canada; and ‖Département de chirurgie, Hôpital Charles-Lemoyne, Greenfield Park, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
Supported by the Canadian Institutes of Health Research (Doctoral research award), the Canadian Health Services Research Foundation (grant: RC2-1460-05), and the Fonds de la recherche en Santé du Québec (grant: 015102).
NTDB data were used with the permission of the Committee on Trauma, American college of Surgeons, NTDB Version 5, Chicago, Illinois, 2005. The content reproduced from the applications remains the full and exclusive copyrighted property of the American Collage of Surgeons. The American Collage of Surgeons is not responsible for any ancillary or derivative works based on the original data, text, tables, or figures.
The funding organizations had no role in the design of the study, collection, analysis, or interpretation of the data; writing of the article; or the decision to submit it for publication. No other funds were received for this study.
Reprints: Lynne Moore, PhD, Unité de traumatologie-urgence-soins intensifs, Centre de recherche du CHA (Hôpital de l'Enfant-Jésus), 1401, 18e Rue, Quebec City, Quebec, Canada G1J 1Z4. E-mail: firstname.lastname@example.org.
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