Elsevier

Annals of Emergency Medicine

Volume 62, Issue 5, November 2013, Pages 486-494.e3
Annals of Emergency Medicine

Health policy/original research
Emergency Department Computed Tomography Utilization in the United States and Canada

Presented as a poster at the Society for Academic Emergency Medicine annual meeting, Boston, MA, June 2011.
https://doi.org/10.1016/j.annemergmed.2013.02.018Get rights and content

Study objective

We compare secular trends in computed tomography (CT) utilization in emergency departments (EDs) in the United States and Ontario, Canada.

Methods

Using a systematic survey in the US (The National Hospital Ambulatory Medical Care Survey) and administrative databases in Ontario, we performed a retrospective study of ED visits from 2003 to 2008. We calculated utilization overall, by visit characteristics, and for 5 clinical conditions in which CT is commonly indicated: abdominal pain, complex abdominal pain (abdominal pain, age ≥65 years, urgent to most urgent triage), admitted complex abdominal pain (abdominal pain, age ≥65 years, urgent to most urgent triage, and admitted to hospital), headache, and chest pain/shortness of breath. US data were weighted to produce national estimates.

Results

On-site CT was available for 97% (95% confidence interval [CI] 95% to 99%) of visits in the United States compared with 80% (95% CI 80% to 80%) in Ontario. Visits were more frequently triaged as higher acuity in the United States than in Ontario, with 15.1% (95% CI 13.9% to 16.4%) of US visits categorized as most urgent versus 11.8% (95% CI 11.8% to 11.8%) in Ontario. The proportion of all ED visits in which CT was performed was 11.4% (95% CI 10.8% to 12.0%) in the United States versus 5.9% (95% CI 5.9% to 5.9%) in Ontario. The proportion for children was 4.7% (95% CI 4.3% to 5.1%) in the United States versus 1.4% (95% CI 1.4% to 1.4%) in Ontario. The rate of visits involving CT per year increased faster from 2003 to 2008 in the United States (odds ratio 2.00; 95% CI 1.81 to 2.21) than Ontario (odds ratio 1.69; 95% CI 1.68 to 1.70). Over time, all subgroups experienced increases in CT rate except Ontario children younger than 10 years, who experienced a significant decrease. United States–Ontario differences in CT proportions were significant among patients presenting with headache, abdominal pain, chest pain/shortness of breath, and complex abdominal pain. Proportions for visits involving admitted complex abdominal pain in the two jurisdictions were indistinguishable: 45.8% in the United States (95% CI 39.9% to 51.7%) versus 44.7% (95% CI 44.4% to 45.0%) in Ontario.

Conclusion

CT was more readily available in US EDs, and US clinicians used the technology more frequently than their colleagues in Ontario for nearly every category of patients, including children. CT utilization increased over time in both jurisdictions, but faster in the United States. Different demographic features between the two jurisdictions, including triage severity, frequency of hospitalization, and availability of CT scanners, likely account for at least some of the differences in CT utilization. Investigation of both clinical and nonclinical reasons for the differences in CT utilization between the United States and Canada would be a fruitful area for further research.

Introduction

Recent studies have demonstrated substantial increases in medical computed tomography (CT) utilization in the United Kingdom,1 Canada,2 the United States, and worldwide.3 Imaging is already common in the emergency department (ED),4 and, each year in the 1990s and early 2000s, utilization increased.5, 6 A recent study of US ED imaging found a near 5-fold increase in scans from 1995 to 2007.7

Guidelines suggest that imaging is a useful diagnostic tool for many acute conditions,8, 9, 10 and it is reasonable for utilization to increase as new indications for testing are developed. However, as medical CT becomes more common, there is concern about the magnitude of imaging-related financial costs and radiation-induced malignancies.11 Concern is especially apt for the pediatric population, which is more susceptible to the effects of ionizing radiation than the adult population.12

The objective of this study was to compare ED CT rates in the United States and Ontario by visit characteristics and reason for visit subgroups. We hypothesized that overall CT utilization would be higher in the United States and increasing faster, and that visits involving high-risk cases of abdominal pain would have similar utilization of CT imaging in both jurisdictions.

Section snippets

Study Design, Setting, and Selection of Participants

This was a retrospective study of ED visits from 2003 through 2008, using a national probability-based survey in the United States and universal administrative health databases in Ontario. We chose these North American jurisdictions because they both house large ethnically diverse populations, and the populations access ED care with near-identical rates per capita13; however, differences in the demographics of the 2 populations are significant. Many of these differences will be discussed in the

Results

All US results are estimates that were generated by weighting complex survey data, whereas all Ontario results are “hard” numbers obtained from administrative databases. Also, results in both jurisdictions are unadjusted for differences in population characteristics.

Limitations

Our 2 data sets are significantly different: US results are national estimates derived from surveys at selected facilities around the nation, whereas Ontario data are “hard” numbers that are extracted from administrative sources at all Ontario hospitals. We were not able to examine patient-level outcomes in the United States, so cross-jurisdictional outcomes could not be compared. Furthermore, we did not use multivariate regression analysis to adjust for potential confounders because this would

Discussion

From 2003 to 2008, CT utilization increased for ED visits in both jurisdictions; and in 2008, 14.6% of all US visits involved CT compared with 7.3% in Ontario. Increases in CT utilization occurred across every subgroup in both jurisdictions, with one important exception: the proportion of visits involving CT for children younger than 10 years decreased. Meanwhile, the proportion for children younger than 10 years in the United States trended toward increase.

For nearly all reason for visit

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    Please see page 487 for the Editor's Capsule Summary of this article.

    Supervising editor: Ellen J. Weber, MD

    Author contributions: CTB, MJV, and MJS conceptualized and designed the study and analyzed and interpreted the data. CTB and MJV acquired the data. CTB drafted the article, and all authors critically revised it for important intellectual content. CTB performed statistical analysis, with administrative and technical support from MTV. MJS supervised the study. CTB takes responsibility for the paper as a whole.

    Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist. Dr. Berdahl is supported by the James G. Hirsch Endowed Medical Student Research Fellowship at the Yale University School of Medicine, and Dr. Schull is supported by the Canadian Health Services Research Foundation and the Commonwealth Fund as a 2010-11 Harkness Fellow.

    Publication date: Available online May 14, 2013.

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