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Greater than 300% Increase in CT Scan Use in ED Over Past Decade


The use of computed tomography scans (CT scans) in U.S. emergency departments (ED) has increased more than 300% over the past decade according to a study from a University of Michigan Health System study.

The study’s findings have been published online ahead of print publication in the Annals of Emergency Medicine and highlighted as a featured article.

Keith Kocher, M.D., M.P.H., a clinical lecturer in U-M Department of Emergency Medicine, and colleagues conducted a retrospective cohort analysis of the ED component of data from the National Hospital Ambulatory Medical Care Survey (NHAMCS), a large nationwide survey of ED services across the United States, from 1996 through 2007.

The primary outcome for this analysis was whether at least 1
CT was performed during an ED visit. The secondary outcome for this analysis was hospital admission or transfer to another facility for further management.

During that 12-year period, 368,680 patient visits yielded results for an estimated 1.29 billion weighted ED encounters, among which an estimated 97.1 million (7.5%) patients received at least one CT scan.

The researchers found that overall, CT scan use during ED visits increased 330%, being much less common early in the study period than in the later time period -- 3.2% of encounters (95% confidence interval [CI] 2.9% to 3.6%) in 1996 compared to 13.9% (95% CI 12.8% to 14.9%) in 2007.

"This means that by 2007, 1 in 7 ED patients got a CT scan," says Kocher. "It also means that about 25% of all the CT scans done in the United States are performed in the ED."

After multivariable adjustment, the researchers found there was a 3-fold increase in the likelihood of CT use over time (adjusted RR 3.11; 95% CI 2.77 to 3.48). No significant different in rates of CT scan use was noted by race or sex, but there was by age. There was a dramatic increase in CT use observed among patients older than 79 years (9.1% in 1996 to 29.1% in 2007) compared to those younger than 18 years (1.1% in 1996 to 5.2% in 2007).

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There was universal increase in CT scan use among the 20 most common complaints presenting to the ED. The largest increases were observed for patients presenting with abdominal pain, in which the likelihood of undergoing a CT was almost 10 times higher in 2007 compared with 1996.

Similarly, the likelihood of receiving a CT scan increased substantially for patients presenting with flank pain (adjusted RR 9.24), chest pain (adjusted RR 5.54), and shortness of breath (adjusted RR 5.28).

By 2007, more than 25% of patients with the following conditions underwent CT during their ED: impairments of nerve, spinal cord or brain function, flank pain, convulsions, vertigo, dizziness or light-headedness, headache, abdominal pain, and general weakness.

"There are risks to overuse of CT scans, because each scan involves radiation -- so if they're done for marginal reasons you have to question why," Kocher says. "For example, patients who complained of flank pain (pain in the side) had an almost 1 in 2 chance of getting a CT scan by the end of the study period. Usually most physicians are doing that to look for a kidney stone, but it's not clear if it's necessary to use a CT scan for that purpose."

He adds, "Also, during the study period, ED visits increased by about 30 percent, while CT use increased 330 percent, meaning the rate of CT use grew 11 times faster than the rate of ED visits."

Patients who received a CT scan in the beginning of the study had a 25% chance of being admitted to the hospital directly from the ED, while by 2007, this rate had been cut in half.

The study doesn't provide the reasons why CT use increased over time -- but "it does make one wonder," Kocher notes.

"I think a lot of the increase is related to changes in how doctors practice medicine and the availability of CT scanners," Kocher says. "They provide lots of information quickly and so doctors and patients see CTs as a means of arriving at diagnoses efficiently and conveniently. Couple that with the fact that CT scanners are commonly housed in or near the ED itself, and the barriers to getting the test done are lower than in the past."

The above story is reprinted (with editorial adaptations by Ramona Bates, MD) from materials provided by University of Michigan Health System.

Image credit.

National Trends in Use of Computed Tomography in the Emergency Department; Keith Kocher, M.D., M.P.H., William J. Meurer, M.D., M.S., Phillip A. Scott, M.D., Brahmajee K. Nallamothu, M.D., M.P.H., Reza Fazel, M.D., M.Sc., Harlan M. Krumholz, M.D., S.M.; Annals of Emergency Medicine. doi:10.1016/j.annemergmed.2011.05.020



This is not surprising, considering the vast leaps that have been made in cat scan imaging, both from a safety perspective as well as the amazing detail of the new imagers. radiology.ucsf.edu/research