[1] HealthPartners Res Fdn, Minneapolis, MN 55440 USA
[2] HealthPartners Med Grp & Clin, Minneapolis, MN USA
[3] Reg Hosp, Dept Emergency Med, St Paul, MN USA
[4] Agcy Healthcare Res & Qual, Rockville, MD USA
[5] Colorado Permanente Med Grp, Clin Res Unit, Denver, CO USA
[6] Univ Colorado, Hlth Sci Ctr, Dept Prevent Med, Denver, CO USA
[7] Univ Colorado, Hlth Sci Ctr, Dept Biometr, Denver, CO USA
[8] Univ Colorado, Hlth Sci Ctr, Div Emergency Med, Denver, CO USA