Finding the medically underserved: a need to revise the federal definition.

The relationship between the primary service area (PSA) of an urban community health center (CHC) program and a federally defined "medically underserved area" (MUA) was assessed. Federal guidelines that most reliably predicted medical underservice were identified. The service area was statistically defined by census tract penetration rates. The MUA was defined by an index of medical underservice (IMU) according to federal parameters of physician supply, poverty level, percentage elderly persons, and infant mortality. An index score was calculated for the country, service area, and each census tract. Analysis by tract determined the most significant discriminating parameters. By excluding two tracts concentrated with managed-care physicians, the service area qualified as an MUA. Tracts that fulfilled MUA and service area criteria were highly associated (p < 0.0001). Only poverty level and infant mortality were useful discriminating parameters. Federal indicators of demand (elderly population) and supply (physicians) did not adequately address issues to access for the medically underserved in urban neighborhoods. Other parameters that might serve as proxies of care access and underserved are discussed.