1. Division of Pediatric Emergency Medicine,
2. Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada;
3. Women and Children's Health Research Institute, Edmonton, Alberta, Canada;
4. Alberta Research Centre for Health Evidence, Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada;
5. Department of Medicine, Durham Veterans Affairs Medical Center, Durham, North Carolina; and
6. Department of Medicine, Duke University, Durham, North Carolina