[1] Oregon Hlth & Sci Univ, Dept Emergency Med, Ctr Policy & Res Emergency Med, 3181 SW Sam Jackson Pk Rd,Mail Code CR 114, Portland, OR 97239 USA
[2] Oregon Hlth & Sci Univ, Dept Emergency Med, Ctr Hlth Syst Effectiveness, Portland, OR 97239 USA
[3] Emory Univ, Rollins Sch Publ Hlth, Dept Hlth Policy & Management, Atlanta, GA 30322 USA
[4] Univ Calif Davis, Dept Emergency Med, Sacramento, CA 95817 USA
[5] Univ Calif San Francisco, San Francisco Gen Hosp, Philip R Lee Inst Hlth Policy Studies, Dept Emergency Med, San Francisco, CA USA
[6] Stanford Univ, Dept Emergency Med, Palo Alto, CA 94304 USA
[7] Stanford Univ, Dept Surg, Palo Alto, CA 94304 USA
[8] Denver Hlth Med Ctr, Dept Emergency Med, Denver, CO USA
[9] Univ Colorado, Sch Med, Colorado Sch Publ Hlth, Dept Epidemiol, Aurora, CO USA
[10] Univ Utah, Sch Med, Dept Pediat, Salt Lake City, UT USA
[11] Univ Washington, Dept Med, Seattle, WA USA
[12] Univ Penn, Leonard Davis Inst Hlth Econ, Dept Emergency Med, Ctr Emergency Care Policy Res,Ctr Clin Epidemiol, Philadelphia, PA 19104 USA