A new method for evaluating trauma centre outcome performance: TRAM-adjusted mortality estimates

Abstract

Objective: To develop a method of evaluating trauma center mortality that addresses the limitations of currently available methodology-Standardized Mortality Ratios (SMRs) based on the Trauma and Injury Severity Score.

Summary of background data: TRISS SMRs have important limitations including inadequate risk adjustment, comparison to an inappropriate standard, lack of consideration for inter- and intrahospital variation, and incomparability across hospitals.

Methods: The methodology was developed using data from a provincial trauma registry with mandatory participation of all trauma centers, uniform inclusion criteria, and standardized data collection methods. Institutional performance was described with estimates of risk-adjusted mortality derived from a hierarchical logistic regression model. Risk adjustment was performed with a risk score generated by the Trauma Risk Adjustment Model (TRAM), as well as a term for incoming transfers and an interaction between transfer and the risk score. Outliers were identified by comparing each hospital to all remaining hospitals.

Results: The study population comprised 88,235 patients including 4731 deaths (5.4%) from 59 trauma centers. Crude mortality varied between 1.3% and 14.3%. TRAM-adjusted mortality estimates varied between 3.7% (95% CI: 3.2%-4.3%) and 6.9% (5.8%-8.2%). Three trauma centers had significantly higher adjusted mortality and one center had statistically significant lower mortality when compared with all other centers.

Conclusions: The proposed method of trauma center profiling offers comprehensive adjustment for patient-level risk factors and consideration of transfer status, is based on comparisons to an internal standard, accounts for inter- and intrahospital variation, and replaces SMRs with estimates of regression-adjusted mortality that are comparable across hospitals. TRAM-adjusted mortality estimates can be used to describe institutional outcome performance and to identify institutional outliers. Such information is the key to identifying ways to improve the quality of modern trauma care.