Study: In-office MRI leads to more back surgeries

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With radiologists and other specialists compiling mounting evidence that orthopedists who acquire MRIs order more tests, a study published online April 21 in Health Services Research now draws a link between the acquisition of in-office MRI and increased surgery rates for low back pain.

A number of recent studies have demonstrated that after the acquisition of an in-office MRI, nonradiologists significantly increase their ordering for the exam. “Increasing use of imaging has also been associated with the potential for ‘treatment cascades’ in which the use of imaging leads to the use of subsequent procedures that are of low value to the patient and, but for receipt of the imaging procedure, would never have been done,” argued Jacqueline Baras Shreibati, MD, MS, from the department of medicine and Laurence C. Baker, PhD, from the department of health research and policy at Stanford University School of Medicine in Stanford, Calif.

Shreibati and Baker evaluated the relationship between the acquisition of an in-office MRI by orthopedic surgeons and primary care physicians and subsequent surgery for patients with low back pain. The authors noted that guidelines dating back to 1994 have advised caution with treatment for low back pain, because of weak correlation between radiographic findings and clinical symptoms and due to a high likelihood that symptoms will improve without treatment.

Shreibati and Baker sampled the Medicare claims of 20 percent of beneficiaries, looking at nonradiologist physicians who began self-referral between 1999 and 2005 and patients presenting with new episodes of nonspecific low back pain.

The average number of MRIs ordered per 100 patients increased by 2.5 following orthopedists’ acquisition of scanners and after controlling for a variety of patient demographics. Primary care physicians exhibited an even larger increase of 35 percent following the acquisition of MRI scanners. Shreibati and Baker also noted that these effects were observed among physicians whose MRI ordering trends were, prior to the acquisition of MR, on par with those of other physicians.

Among patients whose orthopedists acquired MRI during the study period, the probability of undergoing surgery within six months of the exam increased by 34 percent. No significant increase was seen in surgeries among patients of primary care physicians.

Patients of orthopedist MRI acquirers also saw increased costs that significantly exceeded the cost of the additional MRI, averaging an increase of $4,161 over the course of one year. The increase in costs associated with primary care physicians’ acquisition of MRI machines was not significant.

“One important implication of this finding is that the costs of doing these incremental MRIs was much higher than just the cost of the MRI itself (roughly $500), and it could appropriately be taken to include the costs of the additional procedures done as a result of the MRI,” Shreibati and Baker noted.

“Orthopedists and primary care physicians who begin to bill for the performance of MRI procedures, rather than referring patients outside of their practice for MRI, appear to change their practice patterns such that they use more MRI for their patients with low back pain. These increases in MRI use appear to lead to increases in low back surgery receipt among patients of orthopedic surgeons, but not of primary care physicians,” the authors explained.

Shreibati and Baker acknowledged that some of these additional scans and surgeries could have led to improved patient outcomes, while also noting that their findings might generalize differently to conditions other than low back pain.

“Nonetheless, we believe the existence of the relationships we measured should encourage clinicians and policy makers to pay attention to linkages between imaging and treatment use and more generally to the possibility that cascade effects in medicine can occur, and when appropriate, respond accordingly,” Shreibati and Baker concluded.