Spatial analysis of transportation barriers and the availability of primary health care services on avoidable ED admissions in Houston, Texas

Transportation barriers to healthcare services remain a frequently cited, but poorly understood phenomenon. Using Geographical Information Systems (GIS), we examined children's emergency department (ED) admissions for Ambulatory Care Sensitive Conditions (ACSCs) by zip code tabulation area (ZCTA) in Harris County, TX, home to Houston. ACSCs like asthma are frequently used as a proxy for appropriate access to primary health care because with good management, hospitalizations should be avoided. To measure availability of transportation within each of the county's 127 ZCTAs, we developed a Weighted Transportation Index (WTI) consisting of the availability of public transportation in the community and of private vehicle ownership. Public transit availability was estimated by calculating the population of each ZCTA living within ¼ mile of a transit stop. In our research, we examine the relationships between the availability of transportation as measured by the WTI and the availability of primary healthcare services (ratio of primary care providers, PCPs, to population and distance to nearest federally qualified health center, FQHC) on children's ACSC admissions. A spatial regression was developed to estimate the model, controlling for poverty. Findings suggest that the presence of transportation barriers and proximity to FQHCs are highly associated with ACSC rates while greater availability of active PCPs has no impact. By understanding the spatial relationships between transportation barriers and primary care access, factors associated with elevated ACSC rates can be identified and mapped using GIS. Policy makers can target these areas to improve the availability of non-emergency medical transportation and/or deploy new healthcare resources.