By Kate Madden Yee, AuntMinnie.com staff writer

June 25, 2013 -- Little of the geographic variations in emergency department (ED) imaging use can be attributed to physician characteristics such as experience, training, or gender, according to a new study published online in Radiology. In fact, variations in imaging use have more to do with patients.

Almost half -- 47.2% -- of all emergency department visits in the U.S. in 2010 involved imaging, wrote researchers from York University in Toronto and Massachusetts General Hospital (MGH) in Boston. Analyzing and understanding what drives the use of ED imaging is important for several reasons, including the cost-benefit balance for patients, institutions, and payors, as well as the issue of radiation exposure, wrote lead author Hannah Wong, PhD, and colleagues (Radiology, June 25, 2013).

Hannah Wong, PhD
Hannah Wong, PhD, from York University.

"Several studies highlighted substantial variation that exists in imaging rates across and within EDs," the authors wrote. "The presence of this variation suggests that at least some of the increase in the use of ED imaging may be unwarranted."

Variations in ED imaging use can lead to a false assumption that doctors are primarily responsible, said study co-author Dr. Chris Sistrom, PhD.

"There's a lot of concern among radiologists and insurers that imaging may not be providing much value in the emergency department and, in fact, is not only delivering a lot of radiation to patients, but is also boosting healthcare costs," Sistrom told AuntMinnie.com. "The urban myth is that individual doctors have a lot of influence over how much imaging gets done on their emergency department patients -- because they order the exams. We wanted to investigate how much imaging use variability is really caused by doctors."

The team analyzed 88,851 emergency department visits that occurred in 2011 at MGH, using an analytical tool called hierarchical logistic regression to identify multiple predictors of the probability that imaging would be ordered during a given visit.

The overall rate of imaging utilization at MGH's emergency department was 45.4% in 2011, similar to the 2010 national average of 47.2%, according to Wong's group. Study data showed that physician-related factors such as gender, experience, and training did not correlate with imaging use. Instead, patient and visit factors (such as prior visits, referral source, mode of arrival at the ED, and clinical reason for the visit) were the primary predictors of whether an ED patient would receive imaging.

Dr. Chris Sistrom, PhD
Dr. Chris Sistrom, PhD, from MGH.

ED workload also influenced the type of imaging use: When the department was the least busy, the odds of low-cost imaging were 11% higher than the reference standard, while a busier ED had a tendency toward more high-cost imaging.

In any case, once the data were corrected for patient and visit variables, the remaining variation that could be explained by physician practice style was only 1%, Sistrom said.

"This tells us that ER physicians don't differ much from each other in terms of their imaging use," he told AuntMinnie.com.

The study findings show that trying to reduce imaging use in the emergency department by focusing on individual physicians may be misguided, according to Sistrom. It may be better to emphasize order-entry decision-support systems and education that identify specific imaging tests that are commonly ordered, expensive, and of questionable clinical benefit.

"To reduce imaging utilization, a lot of people in quality improvement and medical management might try to identify high outliers and punish them," Sistrom said. "But in settings like the one we studied, that strategy won't get you anything but angry doctors."


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