1. Division of Traumatology, Surgical Critical Care, and Emergency Surgery, University of Pennsylvania Perelman School of Medicine, Philadelphia
2. Department of Biostatistics and Epidemiology, University of Pennsylvania Perelman School of Medicine, Philadelphia
3. Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
4. Columbia University Mailman School of Public Health, New York, New York
5. Department of Emergency Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia