[1] Yale Sch Med, Dept Emergency Med, New Haven, CT 06510 USA
[2] Yale Sch Med, Ctr Outcomes Res & Evaluat, New Haven, CT 06510 USA
[3] Univ Texas Southwestern Med Ctr, Dept Emergency Med, Dallas, TX USA
[4] Stanford Univ, Sch Med, Dept Emergency Med, Stanford, CA USA
[5] Univ Arizona, Coll Med, Dept Emergency Med, Tucson, AZ USA
[6] Harvard Med Sch, Massachusetts Gen Hosp, Dept Emergency Med, Boston, MA USA