Geographic variation in utilization of physician services has been studied in a number of different aspects of medical practice, but there has been very little such work in imaging. Our purpose was to determine how much variation exists in different geographic regions of the country in utilization rates of NDI.
METHOD AND MATERIALS
We used the 2002 Medicare Part B fee-for-service database, which categorizes claims into ten different geographic regions of the country, each of which is designated by a major city within it. All claims in the 70,000 and 90,000 CPT-4 series pertaining to NDI were included. We calculated a utilization rate per thousand for all NDI services performed in each region and determined the proportion performed by radiologists. We also examined utilization growth between 1997 and 2002 among the four specialty groups that are the largest providers of imaging: radiologists, cardiologists, primary care physicians, and surgeons.
In 2002, NDI utilization rates per thousand Medicare beneficiaries ranged from a high of 3959 in the Atlanta region to a low of 2694 in the Seattle region (ratio of the highest to lowest = 1.47). Radiologists’ share of the NDI market ranged from a high of 68% in the Philadelphia region to a low of 58% in the San Francisco region. Between 1997 and 2002, the percent change in overall utilization rates ranged from +32% in Chicago to -4% in Philadelphia. Among the 4 major specialty groups providing imaging, cardiologists showed the largest percentage increases in utilization rates between 1997 and 2002 in all 10 geographic regions, ranging from 38% in Philadelphia to 93% in Chicago.
There is a surprising amount of geographic variation in utilization rates of NDI in the United States; the rate in the highest region is 47% greater than the rate in the lowest. There is also considerable geographic variation in the rapidity with which utilization of NDI is growing. Interestingly, the region showing the least growth in utilization (Philadelphia) is the same one in which radiologists have the largest market share. In all regions of the country, utilization growth is higher among cardiologists than among radiologists or other imaging providers.