Physician Acquisition of Ct, Financial Incentives, and Use of Ct Equipment in the United States

Rationale: In the U.S., advanced imaging equipment has increasingly been acquired by non-radiologist physicians in office-based settings. In this setting, there can be powerful financial incentives favoring the use of the equipment. Some previous studies have suggested that patients of physicians with their own imaging equipment receive imaging much more often – sometimes 3 to 4 times more often – than patients of physicians who do not. However, since these studies are largely cross-sectional, they may not fully account for the underlying propensity of physicians to use imaging. If the physicians most likely to use imaging are most likely to acquire the equipment, the estimated effects may be too large. Nonetheless, in part based on these studies, policy efforts have been proposed that would curtail physician ownership of imaging equipment. Objectives: Using detailed time-series data, we examine provider behavior before and after the acquisition of CT equipment, producing estimates of the impact of physician ownership of imaging equipment that should not be biased by unobserved heterogeneity across physicians. Methodology: This study examines cardiologists and urologists, two specialties in which physician acquisition of CT equipment is common. We identify physicians in these specialties who billed Medicare for the treatment of elderly fee-for-service Medicare beneficiaries between 1999 and 2005. A sample of patient care episodes associated with these physicians was drawn from a 20% sample of Medicare claims data spanning 1999-2005 (N=~6.5 million episodes total). Patient receipt of CT within 7, 30, and 90 days of the initial visit was tracked for each episode. Whether, and if so when, physicians acquired CT equipment was determined based on billing patterns – following previous work, physicians who self-refer for CT or bill Medicare for a CT technical component or global fee are identified as acquiring the equipment. We use episode-level regression analyses to identify changes in patterns of CT use before and after physicians acquire CT equipment. The dependent variables are measures of CT use and the key independent variable is an indicator for whether or not the physician had acquired CT by the time of the initial visit. The regressions include a range of controls for patient demographic and health characteristics, and also include physician fixed effects and controls for month and year of the initial visit. We similarly study changes in total spending for patients. Results: Acquisition of CT equipment is associated with statistically significant increases in CT use. For cardiologists, acquisition of CT approximately doubles the probability that patients receive CT. For urologists, the increase is approximately 60%. Acquisition of CT is also associated with increases in total spending, including additional spending for non-CT tests and procedures. Conclusions: Provider acquisition of CT is associated with increased utilization and higher spending. Effects are large, though smaller than have been inferred from some previous analyses that considered other imaging modalities with different study designs. Policy efforts to encourage efficient utilization of CT in office-based settings may be warranted.