Geographic Variation in the Utilization of Noninvasive Diagnostic Imaging: National Medicare Data, 1998-2007

Objective: This study provides an overview of geographic variation in noninvasive diagnostic imaging utilization in the Medicare population over the period 1998 to 2007.

Materials And Methods: The Centers for Medicare and Medicaid Services Physician Supplier Procedure Summary Master Files for 1998-2007 were the primary data source for the study. Physician Supplier Procedure Summary Master Files are an aggregation of the complete Part B Medicare billing records for all 32-37 million fee-for-service beneficiaries and provide the total number of each type of procedure performed, categorized by geographic regions. For the 10 Centers for Medicare and Medicaid Services geographic regions, we calculated the overall noninvasive diagnostic imaging procedure utilization rate and the ratio of the highest to lowest region (a relative risk statistic) for each year of the study. For the first and last years of the study, we calculated these numbers for 28 noninvasive diagnostic imaging categories.

Results: In 2007, the Atlanta region had the highest utilization rate, with 4.60 procedures per capita, and Seattle had the lowest rate, with 2.99 procedures per capita. The relative risk was 1.54. Over the 10 years of the study, there was little change in the relative utilization rates of regions, and the relative risk ranged between 1.47 and 1.56. In 2007, bone densitometry showed the lowest regional relative risk (1.29), and cardiovascular PET showed the highest regional relative risk (70.2). Cardiovascular noninvasive diagnostic imaging and high-technology, high-cost noninvasive diagnostic imaging (e.g., MRI, PET, and nuclear medicine) showed high regional relative risk.

Conclusion: Regional variation is substantial--about 50% higher in the highest regions than in the lowest regions--but is not huge. Regional variation is increasing slightly. Cardiovascular and high-technology procedures show the greatest regional variation.