Friday, August 17, 2012
Can a test hurt? Early MRI and outcomes
As evidence from across the medical community builds about the potential harm associated with unnecessary medical tests, early MRI for low back pain certainly makes the list of studies that may be more harmful than helpful. In the August 15 issue, Dr. Graves and her colleagues from Seattle published the results of their cohort study comparing clinical and disability-related outcomes in worker’s compensation patients who underwent early (less than 6 weeks after onset of symptoms) MRI and late or no MRI for low back pain. They subdivided these groups into patients with “back sprain” and radiculopathy. Not surprisingly, there were marked baseline differences between the patients with early MRI and late or no MRI, with the patients undergoing early MRI presenting with more severe symptoms. Given these baseline differences, it was also not surprising to see that the early MRI patients in both symptom groups had worse clinical and disability outcomes at one year in the unadjusted analysis. The most interesting finding in the adjusted analysis was that while patients in the “back strain” group had similar clinical outcomes (Pain Intensity, Roland-Morris Disability Questionnaire, SF-36) at one year regardless of MRI timing, patients in the early MRI group were twice as likely to be receiving disability benefits and to be out of work. Early MRI in the radiculopathy patients was generally not associated with clinical and disability outcomes other than the early MRI patients returning to work more slowly. These findings suggest that while “back strain” patients have similar pain and function at one year regardless of imaging, early MRI leads to more disability.
This study represents a very high quality observational study looking at a question that would be hard to study in a randomized fashion. Nonetheless, it has the same limitations of all observational studies, namely that unmeasured baseline differences between the groups could lead to confounding that cannot be controlled with statistical analysis. Additionally, only a minority of potentially eligible patients were included in this study due to failure to enroll or follow-up. While the authors suggest an RCT to study the effect of early MRI on outcomes, it seems that given the findings of this and other studies on this topic, such a study might not be ethically sound.1 The data seem quite clear that early MRI for low back pain in the absence of red flag symptoms or radiculopathy does not lead to better clinical outcomes and probably leads to increased disability. As such, it seems as though there is no need for an RCT comparing early to late or no MRI for patients with acute low back pain. An interesting follow-up to this study would be an analysis focusing on resource utilization and treatment costs between the early and late or no MRI groups, with it seeming likely that the early group would undergo significantly more treatment at a significantly higher cost. The authors of this study should be congratulated for performing a very high quality observational study. It seems as though they have done a good enough job to preclude the need for an expensive RCT.
Please read Dr. Graves’s article in the August 15 issue and the accompanying commentary. Does this article change your approach to ordering an MRI in patients with acute low back pain? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor
1. Webster BS, Cifuentes M. Relationship of early magnetic resonance imaging for work-related acute low back pain with disability and medical utilization outcomes. J Occup Environ Med 2010;52:900-7.