Research from the Institute for Clinical Evaluative Sciences and the Yale School of Medicine in New Haven, Conn., found overall CT rates in the emergency department (ED) are higher and rising faster in the U.S. compared to the province of Ontario. U.S. patients are nearly twice as likely to undergo a CT scan during an ED visit as Canadians.

The results of the study were presented at the Society for Academic Emergency Medicine (SAEM) conference in Boston in last week.

Overall ED CT utilization rates were 11.4 percent in the U.S. and 5.9 percent in Ontario.

“We don’t think that differences in patient populations can explain a two-fold difference in imaging rates,” said Carl Berdahl, MS, 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 U.S. and Ontario found:

• Americans are nearly twice as likely as Ontarians to undergo a CT scan during an ED visit.
• CT rates are more than three times higher in the U.S. 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, such as complex abdominal pain.
• CT rates for children under age five in EDs are higher and rising in the U.S., 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,” said Michael Schull, MD, co-author and senior scientist at the Institute for Clinical Evaluative Sciences in Ontario, Canada. “Our results call into question whether imaging utilization is appropriate in either region.”