1 Division of Pediatric Emergency Medicine, Montreal Children's Hospital, Montreal, Quebec, Canada.
2 Health Centre.
3 Department of Biostatistics, Epidemiology and Occupational Health, McGill University, Montreal, Quebec, Canada.
4 Division of Pediatric Emergency Medicine, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois.
5 Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois.
6 Division of Emergency Medicine, Department of Pediatrics, British Columbia Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada.
7 Section of Pediatric Emergency Medicine, Department of Pediatrics.
8 Sections of Pediatric Emergency Medicine and Gastroenterology, Departments of Pediatrics and Emergency Medicine, Cumming School of Medicine, University of Calgary, Calgary, Canada.
9 Departments of Emergency Medicine and Pediatrics, University of California, Davis School of Medicine, Sacramento, California.