Mapping healthcare access for vulnerable populations: An analysis of utilization at a mobile medical clinic using geographic information systems

Background: Medical mobile clinics (MMCs) are innovative public health strategies that are documented as effective forms of healthcare delivery to reduce geographic, structural, and social barriers to care, particularly in vulnerable populations. However, information on distribution of MMC client origin and travel behaviors is limited. This study uses Geographic Information System (GIS) to map origins of clients utilizing MMC services in New Haven, CT, and to examine the importance of GIS in developing a spatial understanding of health-seeking and health-utilization behaviors. Methods: Client addresses from 2004 through 2011 were geocoded and aggregated to the census block group. MMC sites were then mapped and buffered to create a 5-mile catchment areas. Client demographics and services utilization within and without this radius were compared using Wilcoxon rank sum tests. Results: Of 7,700 total clients, 7056 (91.6%) lived within 5-miles of a MMC site (proximate), and 644 (8.4%) were outside (remote). Remote clients were significantly more likely to be White (53.3% vs. 22.5%, p<0.001), inject drugs (27.5% vs. 15.7%, p<0.001), receive opioid substitution therapy (18.9% vs. 7.7%, p<0.001), be HIV-infected (11.8% vs. 8.6%, p=0.006), and report mental illness (32.2% vs. 22.9%, p<0.001). Conclusions: Our analysis has found that CHCV's unique provision of targeted services draws clients far beyond local communities. Thus, GIS can provide important insight into the provision and utilization of unique services delivered in urban healthcare settings to marginalized populations with specific needs.