[1] Ottawa Hosp, Dept Emergency Med, Clin Epidemiol Unit, F647,1053 Carling Ave,Box 685, Ottawa, ON K1Y 4E9, Canada
[2] Univ Ottawa, Ottawa, ON, Canada
[3] Ottawa Hosp, Dept Med, Div Neurol, Ottawa, ON, Canada
[4] Ottawa Hosp Res Inst, Clin Epidemiol Program, Ottawa, ON, Canada