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Americans nearly twice as likely as Canadians to undergo a CT scan during an ED visit: study


American patients are nearly twice as likely to undergo a CT scan during an Emergency Department (ED) visit as Canadians. New research from the Institute for Clinical Evaluative Sciences (ICES) and the Yale School of Medicine found overall CT rates in the ED are higher and rising faster in the US compared to the province of Ontario. The results of this study are being presented at The Society for Academic Emergency Medicine (SAEM) conference in Boston, MA in June.

“We don’t think that differences in patient populations can explain a two-fold difference in imaging rates,” says Carl Berdahl, a Yale medical student. “Emergency Department patients in America are unlikely to be that much sicker than their Canadian counterparts.”

This retrospective population-based study of ED visits from 2003 to 2008 in the US and Ontario found:

  • Americans are nearly twice as likely as Ontarians to undergo a CT scan during an ED visit.
  • Overall CT rates in the ED are higher and rising faster in the US compared to Ontario.
  • CT rates are more than 3 times higher in the US for some groups (e.g. trauma patients) compared with Ontario, yet the rates are nearly identical in patients who have the clearest clinical reason for a CT.
  • Since children are at particular risk from CT radiation exposure, a concerning finding is that CT rates for children under 10 in EDs are higher and rising in the US, while they remained flat or declined in Ontario.

“These large differences in imaging rates suggest that practice and incentives built into our health systems are affecting clinical decision-making,” says Dr. Michael Schull, co-author and Senior Scientist at ICES. “Our results call into question whether imaging utilization is appropriate in either region.”

Author Block: Carl T. Berdahl, BA, Marian J. Vermeulen, David B. Larson, Michael J. Schull.

The study “A Tale of Two Trends: Utilization of Computed Tomography in American and Canadian Emergency Departments” is being presented in Boston, MA at the SAEM conference.

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.



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