[1] Univ Alabama Birmingham, Dept Emergency Med, Sch Med, Birmingham, AL 35249 USA
[2] Mem Sloan Kettering Canc Ctr, Dept Epidemiol & Biostat, New York, NY 10021 USA
[3] Univ Washington, Dept Biostat, Clin Trials Ctr, Seattle, WA 98195 USA
[4] Univ Ottawa, Dept Emergency Med, Ottawa, ON, Canada
[5] Univ Ottawa, Ottawa Hosp, Res Inst, Ottawa, ON, Canada
[6] Univ Toronto, St Michaels Hosp, Dept Med,Rescu, Keenan Res Ctr,Li Ka Shing Knowledge Inst,Div Eme, Toronto, ON M5B 1W8, Canada
[7] Johns Hopkins Univ, Dept Med, Baltimore, MD USA
[8] Univ Pittsburgh, Dept Emergency Med, Pittsburgh, PA USA