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Nearly half of primary care patients with low back pain (LBP) receive lumbar x-rays during the acute-care episode. These x-rays are not highly sensitive or specific for detection of spinal malignancies. However, cancer is a rare cause of LBP in these patients. The few back cancer cases detected with rapid magnetic resonance imaging (MRI) over x-ray do not justify the extra costs of routine MRI among LBP primary care patients, according to the authors of a recent study supported in part by the Agency for Healthcare Research and Quality (HS09499).
Doctors should use findings that are red flags for cancer, such as history of cancer, unexplained weight loss, failure of conservative therapy to alleviate back pain, and elevated erythrocyte (red blood cell) sedimentation rate before referral for rapid MRI. Rapid MRI might also be more valuable in certain subgroups, such as breast cancer patients with nonspecific back pain and known metastasis to the bone, suggests William Hollingworth, Ph.D., of the University of Washington School of Medicine.
Dr. Hollingworth and his colleagues developed a model to calculate the cost per cancer case detected and cost per quality-adjusted life year (QALY) using rapid MRI versus plain x-ray among a hypothetical group of primary care patients with LBP. The rapid MRI strategy was more expensive due to higher initial imaging costs and the additional patients who required conventional MRI (which has better image resolution) and biopsy to confirm rapid MRI findings.
The average cost per patient for rapid MRI was $282 compared with $147 for plain x-ray. The rapid MRI strategy was more sensitive for detecting cancer than the x-ray strategy (62 vs. 55 percent). However, because of low prevalence of cancer-related LBP, this generates less than one extra cancer case detected per 1,000 patients imaged. Thus, the incremental cost per case detected using rapid MRI was high at $213,927. Rapid MRI also resulted in only a small increase in quality survival (0.00043 QALYs) at a cost of $296,176 more per QALY.
See "Rapid magnetic resonance imaging for diagnosing cancer-related low back pain," by Dr. Hollingworth, Darryl T. Gray, M.D., Sc.D., Brook I. Martin, B.S., and others, in the April 2003 Journal of General Internal Medicine 18, pp. 303-312.
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