[1] Yale Univ, Dept Emergency Med, 464 Congress Ave,Ste 260, New Haven, CT 06519 USA
[2] Yale Drug Use Addict & HIV Res Scholars Program, New Haven, CT USA
[3] Univ Penn, Perelman Sch Med, Dept Emergency Med, Ctr Emergency Care Policy & Res, Philadelphia, PA 19104 USA
[4] Univ Penn, Perelman Sch Med, Dept Biostat Epidemiol & Informat, Philadelphia, PA 19104 USA
[5] Univ Penn, Leonard Davis Inst Hlth Econ, Philadelphia, PA 19104 USA
[6] Univ Penn, Penn Injury Sci Ctr, Philadelphia, PA 19104 USA