Diagnostic imaging overuse in children evaluated in emergency departments (EDs) is a potential target for reducing low-value care. Variation in practice patterns across Canada and the United States stemming from organization of care, payment structures, and medicolegal environments may lead to differences in imaging overuse between countries.To compare overall and low-value use of diagnostic imaging across pediatric ED visits in Ontario, Canada, and the United States.This study used administrative health databases from 4 pediatric EDs in Ontario and 26 in the United States in calendar years 2006 through 2016. Individuals 18 years and younger who were discharged from the ED, including after visits for diagnoses in which imaging is not routinely recommended (eg, asthma, bronchiolitis, abdominal pain, constipation, concussion, febrile convulsion, seizure, and headache) were included. Data analysis occurred from April 2018 to October 2018.Diagnostic imaging use.Overall and condition-specific low-value imaging use. Three-day and 7-day rates of hospital admission and those admissions resulting in intensive care, surgery, or in-hospital mortality were assessed as balancing measures.A total of 1 783 752 visits in Ontario and 21 807 332 visits in the United States were analyzed. Compared with visits in the United States, those in Canada had lower overall use of head computed tomography (Canada, 22 942 [1.3%] vs the United States, 753 270 [3.5%]; P < .001), abdomen computed tomography (5626 [0.3%] vs 211 018 [1.0%]; P < .001), chest radiographic imaging (208 843 [11.7%] vs 3 408 540 [15.6%]; P < .001), and abdominal radiographic imaging (77 147 [4.3%] vs 3 607 141 [16.5%]; P < .001). Low-value imaging use was lower in Canada than the United States for multiple indications, including abdominal radiographic images for constipation (absolute difference, 23.7% [95% CI, 23.2%-24.3%]) and abdominal pain (20.6% [95% CI, 20.3%-21.0%]) and head computed tomographic scans for concussion (22.9% [95% CI, 22.3%-23.4%]). Abdominal computed tomographic use for constipation and abdominal pain, although low overall, were approximately 10-fold higher in the United States (0.1% [95% CI, 0.1%-0.2%] vs 1.2% [95% CI, 1.2%-1.2%]) and abdominal pain (0.8% [95% CI, 0.7%-0.9%] vs 7.0% [95% CI, 6.9%-7.1%]). Rates of 3-day and 7-day post-ED adverse outcomes were similar.Low-value imaging rates were lower in pediatric EDs in Ontario compared with the United States, particularly those involving ionizing radiation. Lower use of imaging in Canada was not associated with higher rates of adverse outcomes, suggesting that usage may be safely reduced in the United States.
