Cohort identification and episode of care definition
concussion, head injuries
DISEASE
Administrative data were drawn from the Alberta Ambulatory Care Reporting System, National Ambulatory Care Reporting System, and physician claims. These databases contain information on all medical services received by publicly insured residents of Alberta. The identified cohort included children ages 5–17 who made at least one visit to the 5 sites’ EDs during the trial and received diagnoses for concussion or other head injuries, consistent with the Centers for Disease Control and Prevention surveillance definition (see Supplemental Table 1 for codes and rationale) [