• K John McConnell, Craig D Newgard, Richard J Mullins, Melanie Arthur, and Jerris R Hedges.
• Center for Policy and Research in Emergency Medicine, Department of Emergency Medicine, Oregon Health and Science University, Portland, OR, USA.
• Health Serv Res. 2005 Apr 1;40(2):435-57.

ObjectiveTo determine whether head-injured patients transferred to level I trauma centers have reduced mortality relative to transfers to level II trauma centers.Data Source/Study SettingRetrospective cohort study of 542 patients with head injury who initially presented to 1 of 31 rural trauma centers in Oregon and Washington, and were transferred from the emergency department to 1 of 15 level I or level II trauma centers, between 1991 and 1994.Study DesignA bivariate probit, instrumental variables model was used to estimate the effect of transfer to level I versus level II trauma centers on 30-day postdischarge mortality. Independent variables included age, gender, Injury Severity Scale (ISS), other indicators of injury severity, and a dichotomous variable indicating transfer to a level I trauma center. The differential distance between the nearest level I and level II trauma centers was used as an instrument.Principal FindingsPatients transferred to level I trauma centers differ in unmeasured ways from patients transferred to level II trauma centers, biasing estimates based on standard statistical methods. Transfer to a level I trauma center reduced absolute mortality risk by 10.1% (95% confidence interval 0.3%, 22.2%) compared with transfer to level II trauma centers.ConclusionsPatients with severe head injuries transferred from rural trauma centers to level I centers are likely to have improved survival relative to transfer to level II centers.

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