[1] Childrens Hosp Eastern Ontario, Dept Pediat, Ottawa, ON, Canada
[2] Ottawa Hosp Res Inst, Clin Epidemiol Program, Ottawa, ON, Canada
[3] Univ Colorado, Sch Med, Dept Pediat, Aurora, CO USA
[4] Univ Calgary, Cumming Sch Med, Dept Pediat, Calgary, AB, Canada
[5] Univ Calgary, Cumming Sch Med, Dept Emergency Med, Calgary, AB, Canada
[6] Univ Calgary, Cumming Sch Med, Dept Physiol & Pharmacol, Calgary, AB, Canada
[7] Univ Calgary, Alberta Childrens Hosp Res Inst, Calgary, AB, Canada
[8] Univ Ottawa, Sch Epidemiol Publ Hlth & Prevent Med, Ottawa, ON, Canada