Defining Primary Care Shortage Areas: Do GIS-based Measures Yield Different Results?

Area of Science:

• Health Services Research
• Geographic Information Systems
• Public Health

Background:

• Accurate identification of primary care shortage areas is crucial for resource allocation.
• Traditional methods for designating shortage areas may not fully capture spatial access to care.

Purpose of the Study:

• To compare primary care shortage area designations using GIS-based physician-to-population ratios (PPRs) versus traditional bounded-area PPRs.
• To assess the agreement between GIS-based and bounded-area methods in identifying geographic primary care shortage areas.

Main Methods:

• Constructed two shortage area indicators: a bounded-area indicator and a GIS-based indicator measuring spatial proximity to primary care physicians (PCPs).
• Utilized geocoded PCP locations and census block population data from one US state.
• Examined agreement and disagreement between the two indicators across different geographic areas.

Main Results:

• High agreement was observed between GIS-based and bounded-area indicators for the majority of the population (95% full sample, 98% urban sample).
• Agreement was lower in rural areas (87% of the rural population), indicating potential underestimation of shortages by bounded methods.
• Disagreement was more prevalent due to the border-crossing problem.

Conclusions:

• GIS-based PPRs provide similar primary care shortage area determinations compared to bounded-area PPRs.
• The disagreement rates found in this study were lower than those reported in previous research.
• While GIS methods offer a more nuanced view, particularly in rural settings, overall concordance with traditional methods is high.