Using Geographic Information Systems to Evaluate the Use of Estimated Drive Times as Rational Service Areas for Primary Care

Background: Health care service areas have been utilized to assess use of health care services and evaluate population health indicators. Primary Care Service Areas (PCSAs) are examples of health care service areas, made up of contiguous ZIP Code Tabulation Areas and based almost entirely on Medicare usage. PCSAs have been proposed as rational service areas to assess health indicators and socioeconomic variables in order to evaluate primary care shortages and make federal and state policy and funding decisions. We propose that in rural areas, service areas based on average drive times to primary care providers are more rational for the populations in terms of geographic accessibility and for assessing health outcomes. Data and Methods: Utilizing geographic information systems, 30-minute estimated drive time service areas were calculated based on road networks around primary care providers selected from the 2011 American Medical Association's Physician's Masterfile and compared to 33 rural PCSAs in Missouri. Population and demographic coverage were derived from the 2010 Decennial Census at the block level. The comparisons were made based on the difference in area and population covered by both methods. Results: Some PCSAs fell completely within a 30-minute travel time, while other PCSAs include both large areas and populations outside of the travel time service area possibly causing insufficient geographic access to primary care services. Conclusions: Service areas based on predefined geographies are sometimes sufficient for assessing access to primary care, but often include populations that may not have sufficient geographic access to the primary care services.