By Trevor Stokes
NEW YORK (Reuters Health) - Emergency patients received nearly twice as many CT scans in the U.S. as in Ontario in recent years, according to a new study that also found use of the high-powered X-rays is rising in both countries.
Doctors use CT scans to get a clearer image of the interior of the body than regular X-rays can provide, but the imaging is costly and exposes patients to higher levels of radiation - raising concern about cancer risks from repeated CTs, especially in children.
"Our study wasn't able to look at whether this was a good thing or a bad thing for patients in terms of patient outcome, but I think it does beg the question: Since the technology is available in both countries, why is it being used twice as often in the U.S.?" said study author Dr. Carl Berdahl, emergency medicine resident at Los Angeles County University of Southern California Medical Center.
He and his colleagues compared 699 million U.S. emergency department medical records to 26 million from Ontario, covering the years 2003 to 2008.
Overall, nearly 1 out of every 9 U.S. emergency patients received a CT scan, compared with 1 in 17 Ontario emergency patients.
Patients being treated for trauma - for instance to the head or abdomen - received CT scans nearly four times as often in the U.S. compared with Ontario, according to the results published in the Annals of Emergency Medicine.
However, in both the U.S. and Ontario, an equal proportion - 45 percent - of the sickest non-trauma emergency patients received CT scans.
During the study period, CT scans of children aged 10 and younger increased in the U.S. while at the same time decreasing in Canada.
The researchers focused on how often emergency doctors used CT scans to assess patients with abdominal pain, headache, chest pain or shortness of breath.
The U.S. data came from estimates from national surveys, whereas the Ontario data came from the provincial registry that closely tracks emergency medicine.
"We use the technology in the U.S. a lot more and expose more children to radiation; but we're not sure at this stage whether one strategy may be better than the other," said Berdahl.
Dr. Keith E. Kocher, an expert in emergency use of CT scans and instructor of emergency medicine at the University of Michigan, wasn't surprised with the results, and said the study could help sharpen the focus on what is driving differences between the U.S. and Canada in the use of CT for diagnosis.
While the study could not discern whether the U.S. overtested or Ontario undertested, Kocher said evidence from other studies suggests that U.S. doctors scanned emergency patients excessively.
Based on those studies, several factors may drive ER doctors in the U.S. to overuse CT: lack of time for well-thought-out decisions, unfamiliarity with patients, fear of litigation and the technological imperative that a doctor is more likely to use a CT scanner if the machine is nearby.
Nearly all U.S. patients (97 percent) had access to a CT scanner, while 80 percent of Ontarians had access.
Physicians and others may come to realize that they're overtesting and also at some point, CT scan use will stop growing because of the finite number of eligible patients, he said.
Non-radioactive alternatives to CT scans include ultrasound and MRI. Ultrasounds, like those used for expecting mothers, give less information and are not available in ERs in small hospitals. MRIs give detailed information, but are very costly and not available in most ERs, experts noted.
Berdahl and colleagues are looking into the feasibility of using radiation-free ultrasound and MRIs to help diagnose appendicitis in children.
Regardless of the disparities between the U.S. and Ontario, "in both places, they're doing too many studies (CT scans)," said Howard Forman, health economist at Yale University and practicing emergency/trauma radiologist.
Other research has found unnecessarily repeated CT scans, patients who didn't meet the criteria to have a CT scan and, more rarely, CT scans that get ordered because of miscommunication, noted Forman, who was not involved in the current study.
"In some instances, the appropriate study (CT scan) is done, but waiting an extra three or six hours may have avoided the need for doing the study," he told Reuters Health. "Sometimes we're so quick to want to image problems that we're not willing to wait to see if the symptoms resolve on their own."
The U.S. system also depends on high throughput of patient and in many cases, fee for service, which can give doctors incentives to scan patients instead of waiting symptoms out, experts said.
"In the U.S. system, there are strong incentives to get the CT scan done now and send the patient home or to the operating room," Forman said.
SOURCE: bit.ly/17EcP8t Annals of Emergency Medicine, online May 16, 2013.