1 Division of Pediatric Emergency Medicine, Department of Pediatrics, Montreal Children's Hospital, McGill University Health Centre, Montreal, Quebec, Canada.
2 Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada.
3 Department of Pediatrics, Health Sciences Center, Children's Hospital Winnipeg, University of Manitoba, Winnipeg, Manitoba, Canada.
4 Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada.
5 Sections of Pediatric Emergency Medicine and Gastroenterology, Departments of Pediatrics and Emergency Medicine, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.