A propensity score analysis of prehospital factors and directness of transport of major trauma patients to a level I trauma center.

Background: Indications for direct transport may be strongly related to risk of future health outcomes, and these indications may not be adequately controlled by considering only in-hospital variables. This study was designed to identify prehospital factors associated with directness of transport.
Methods: The study included 2,062 patients treated at a Level I trauma center between January 1, 2006, and December 31, 2007. The outcome of interest was directness of transport to a Level I trauma center. A propensity score analysis was used to identify demographic, clinical, distance, and other injury scene-related variables associated with the probability of direct transport.
Results: A total of 1,459 patients were directly transported to the Level I trauma center and 603 were transferred from lower level facilities. Patients were more likely to be transported directly if they had lower Glasgow Comma Scale scores, had penetrating injuries, were involved in traffic-related injuries, were closer to a Level IV or I trauma center, and if an advanced life support emergency medical service agency transported them from the scene. Patients were more likely to initially stop if they required advanced airway management, met at least one anatomic criterion, were further away from a Level I trauma center, or closer to an intermediate facility.
Conclusions: Confounding due to unadjusted prehospital factors may be present in studies evaluating the impact of directness of transport on short-term mortality outcomes. Propensity score analysis of treatment indications provides an additional and efficient method to reduce this bias.