1 Department of Emergency Medicine, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
2 Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
3 Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Institute of Health Policy, Management and Evaluation, Department of Medicine, University of Toronto, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.