Trauma system accreditation and patient outcomes in British Columbia: an interrupted time series analysis

Objective: We aim to assess the impact of several accreditation cycles of trauma centers on patient outcomes, specifically in-hospital mortality, complications and hospital length of stay. Design: Interrupted time series. Setting: British Columbia, Canada. Participants: Trauma patients admitted to all level I and level II trauma centers between January 2008 and March 2018. Exposure: Accreditation. Main Outcomes and Measures: We first computed quarterly estimates of the proportions of in-hospital mortality, complications and survival to discharge standardized for change in patient case-mix using prognostic scores and the Aalen-Johansen estimator of the cumulative incidence function. Piecewise regressions were then used to estimate the change in levels and trends for patient outcomes following accreditation. Results: For in-hospital mortality and major complications, the impact of accreditation seems to be associated with short- and long-term reductions after the first cycle and only short-term reductions for subsequent cycles. However, the 95% confidence intervals for these estimates were wide, and we lacked the precision to consistently conclude that accreditation is beneficial. Conclusions: Applying a quasi-experimental design to time series accounting for changes in patient case-mix, our results suggest that accreditation might reduce in-hospital mortality and major complications. However, there was uncertainty around the estimates of accreditation. Further studies looking at clinical processes of care and other outcomes such as patient or health staff satisfaction are needed.