Abstract
BACKGROUND: Most quality metrics focus on underuse of services, leaving unclear what factors are associated with potential overuse. METHODS: We analyzed Medicare claims from 2000-2002 and 2004-2006 for 35 039 fee-for-service Medicare beneficiaries with acute low back pain (LBP) who were treated by 1 of 4567 primary care physicians responding to the 2000-2001 or 2004-2005 Community Tracking Study Physician Surveys. We modified a measure of inappropriate imaging developed by the National Committee on Quality Assurance. We characterized the rapidity (<28 days, 29-180 days, none within 180 days) and modality of imaging (computed tomography or magnetic resonance imaging [CT/MRI], only radiograph, or no imaging). We used ordered logit models to assess relationships between imaging and patient demographics and physician/practice characteristics including exposure to financial incentives based on patient satisfaction, clinical quality, cost profiling, or productivity. RESULTS: Of 35 039 beneficiaries with LBP, 28.8% underwent imaging within 28 days and an additional 4.6% between 28 and 180 days. Among patients who received imaging, 88.2% received radiography, while 11.8% received CT/MRI as their initial study. White patients received higher levels of imaging than black patients or those of other races. Medicaid patients received less rapid or advanced imaging than other patients. Patients had higher levels of imaging if their primary care physician worked in large practices. Compared with no incentives, clinical quality-based incentives were associated with less advanced imaging (10.5% vs 1.4% for within 28 days; P < .001), whereas incentive combinations including satisfaction measures were associated with more rapid and advanced imaging. Results persisted in multivariate analyses and when the outcome was redefined as the number of imaging studies performed. CONCLUSIONS: Rapidity and modality of imaging for LBP is associated with patient and physician characteristics but the directionality of associations with desirable care processes is opposite of associations for measures targeting underuse. Metrics that encompass overuse may suggest new areas of focus for quality improvement.