Measuring the impact of trauma care on survival: rates of preventable death, effectiveness, and efficacy.

This paper focuses on the appropriateness of outcome measures to evaluate trauma care. The preventable death rate (PDR), based on the study of deceased patients only, has been the traditional measure of the impact of trauma care on improving the survival of patients with severe trauma. Another measure frequently used in other ares of evaluation research is the effectiveness rate--i.e. the survival rate in the total population of severe trauma patients. Because both the PDR and the effectiveness rate vary with the proportion of patients who would die even under conditions of optimal care, these two measures can be misleading. We illustrate their inadequacy by using published data on the impact of regionalization of trauma care. We propose the use of a third outcome measure of the impact of trauma care on survival, the efficacy rate--i.e. the survival rate among severe trauma patients with a potential for survival. Evaluation of trauma care should also measure outcomes other than survival and need not be restricted to patients with the most severe trauma. Evaluation of trauma care therefore requires outcome measures, such as the efficacy rate, which are based on the population at risk of manifesting the outcome of interest.