Big Bump in Emergency Department Use of CT Scans

By Clive Riddle, August 11, 2011

Keith Kocher, M.D., M.P.H., a clinical lecturer in U-M Department of Emergency Medicine, was lead author for a 14 page paper just published in the August issue of Annals of Emergency Medicine:  “National Trends in Use of Computed Tomography in the Emergency Department” [doi:10.1016/j.annemergmed.2011.05.020]. They examined national data for CT Scan use in EDs from 1996 to 2007, using CDC’s National Hospital Ambulatory Medical Care Survey, that involved 1.29 billion weighted records of emergency visits , 97.1 million of which included patients who received a CT scan.

Kocher’s team found that the “rate of CT use grew 11 times faster than the rate of ED visits during the study period. The study also showed that the use of CT scans was less common early in the study period, but rose significantly over time. Just 3.2 percent of emergency patients received CT scans in 1996, while 13.9 percent of emergency patients seen in 2007 received them.”

Doctor Kocher tells us "this means that by 2007, 1 in 7 ED patients got a CT scan. It also means that about 25 percent of all the CT scans done in the United States are performed in the ED. 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. 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. I think a lot of the increase is related to changes in how doctors practice medicine and the availability of CT scanners. 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."

On the other hand, they note that “patients who received a CT scan in the beginning of the study had a 25 percent chance of being admitted to the hospital directly from the ED, while by 2007, this rate had been cut in half…[and that] this difference suggests that CT use may also prevent ICU admissions, perhaps shifting these hospitalizations toward a non-ICU bed. In general, however, the effect of CT use in the ED and hospitalization or transfer appeared to diminish after 2003 when the adjusted rate flattened and stabilized between 10.8% and 12.8% despite a continuing increase in overall CT use.”

They also note that “for all of the 20 most common reasons patients came to the ER for treatment, the study found that CT use increased during the study period. However, CT use was particularly high for the following complaints” [% of visits with CT scans indicated] impairments of nerve, spinal cord or brain function (50.7%); flank pain (43.3%); convulsions (38.9%); vertigo, dizziness or light-headedness (36.3%); headache (32.5%); abdominal pain (31.7%); and general weakness (25.6%).