A new study has found that patients are more likely to have magnetic resonance imaging scans that indicate nothing is wrong if they are referred by a doctor who owns the machine. The scientists conclude that doctors with a financial interest in the machines may be more likely to order M.R.I.s even when clinical findings suggest they are unnecessary.
The researchers reviewed referrals for knee M.R.I. examinations made by two physician groups, one with a financial interest in a scanner, the other without. There were 350 referrals in each group, and none of the patients had had a previous M.R.I. or knee surgery. The study was published online in Radiology.
Of the 700 examinations, 205 had negative results, indicating no abnormalities. But the rate of negatives was 33 percent in patients referred by doctors who owned the machine, compared with 25 percent of patients referred by those without a financial stake in the device.
There were no significant differences between the groups in the age or sex of the patients, or the training or number of years in practice of the doctors. The machines were all in the same 50-mile radius so convenience was eliminated as a possible reason for referral.
“There is a potential for bias in certain settings,” said Dr. Matthew P. Lungren, the study’s lead author and a fellow in radiology at Duke. “The doctor should be transparent and acknowledge his interest. That should be disclosed.”
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