Patients undergoing MRI exams on their knee are more likely to have a negative finding if the physician who referred them for imaging had a financial stake in the imaging equipment used, according to a study published online Sept. 17 in Radiology. 

The study adds further evidence to the role self-referral plays in determining imaging utilization.

“These findings suggest that there is a different threshold for ordering MRI examinations which may be due to financial incentive,” wrote authors Matthew P. Lungren, MD, of the Interventional Radiology Translational Research Lab at Duke University Medical Center in Durham, N.C., and colleagues.

The practice of a non-radiologist physician referring a patient to an imaging facility in which they or a partner has a financial interest is considered self-referral. Prior studies have demonstrated increased imaging use from practices that self-refer, which could mean imaging is being overused for financial gain, though this conclusion has generated controversy. Defenders of self-referral have criticized previous analyses for not taking into account the complicated nature of referral relationships and the possibility that patient characteristics may play a role.

Lungren and colleagues’ study—the first, to their knowledge, that examined self-referral in orthopedic knee MRI—aimed to determine whether self-referral was more or less likely to result in a positive imaging finding. They reviewed 700 consecutive diagnostic knee exams interpreted at an academic radiology practice between January and April 2009, with half being ordered by a group that had a financial interest in the MRI equipment use and half coming from a second group that had no financial interest.

Results showed that knee MRIs ordered by the group with a financial interest were 33 percent more likely to be negative, suggesting a high number of potentially unnecessary exams, according to the authors. Of 205 negative exams, 117 were in the self-referral group. A total of 33 percent of patients in that group had negative scan results, compared with 25 percent of the group referred by physicians with no financial interest.

There was no significant difference in the number of abnormalities per positive scan between the two groups, which likely means the distribution and severity of abnormalities was similar. Additionally, there was no difference in mean age and the patients came from similar geographic locations, suggesting the results were not biased by difference in the patient groups.

“This increase in unnecessary costs is of paramount importance in the current national conversation regarding health care cost and implementation,” Lungren said in a release. From 2004 through 2010, there was an 80 percent increase in the number of self-referred MRI services compared with an increase of 12 percent for non-self-referred MRI services. U.S. Government Accountability Office estimates have indicated that in 2010, there were 400,000 more referrals for advanced imaging services than there would have been had the ordering groups not been self-referring, costing Medicare an additional $109 million.