Ranking of trauma center performance: the bare essentials

Abstract

Background: Evaluation of trauma center performance has been limited to comparisons of observed versus expected mortality using trauma and injury severity score methodology. Few studies have focused on identifying top performers. In part, this is due to the perceived need for extensive data required to adequately risk adjust. We set out to identify the patient and injury-related factors that most affect case-mix across centers and thus are most likely to alter assessments of hospital performance.

Methods: One hundred ninety trauma centers contributing data to the National Trauma Databank (NTDB) during 2004 to 2005 were used for hospital rankings (n = 169,929 patients). Trauma centers were ranked by crude mortality. We then added variables [injury severity score {ISS}, systolic blood pressure {SBP}, mechanism, age, gender, comorbidities, body region abbreviated injury scale {AIS}] singly to a risk-adjustment model to obtain adjusted probability of death. Trauma centers were then ranked again. The variable that affected rankings the greatest was kept and the process was repeated in an iterative fashion until the incremental change in ranks was minimal.

Results: ISS accounted for the most variation in mortality rates across trauma centers, shown by the large rank change with addition of ISS to the model. Specifically, when ISS was taken into consideration, 92% of trauma centers changed their rank by >/=3 and almost half their quartile rank by at least 1. In lesser order of importance, age, SBP, head AIS, mechanism, gender, and abdominal AIS were relevant to adjust for case mix.

Conclusions: Trauma center rankings are affected by few parameters, reflecting their relationship to mortality and their relative frequencies. Complex risk adjustment methodology is not required to address differences in case mix. Data abstraction for the purpose of comparing trauma center performance should focus on ensuring that at minimum, these variables are collected with a high degree of accuracy.