Exploring the potential link between Medicaid access restrictions, physician location, and health disparities

To determine whether a given doctor treating Medicaid patients is likely to practice in a predominantly minority area, and whether a minority patient is likely to be treated by a physician who is heavily influenced by Medicaid policy decisions.

Retrospective pharmacy claims database analysis combined with zip-5-level demographic analysis.

Data extracted from a large prescription claims database were used to categorize all active prescribers in the United States by the proportion of prescription claims paid by state Medicaid programs from May 31, 2003, to April 30, 2004. US Census data from 2000 were used to assess the ethnic composition of each physician's zip code. Descriptive analyses were conducted to explore any associations between zip code racial composition and proportion of prescriber prescription claims adjudicated by state Medicaid programs.

Physicians with more than 75% of their prescriptions adjudicated through Medicaid versus those with fewer than 1% of their prescriptions adjudicated through Medicaid practiced in zip codes that were 47% versus 24% nonwhite, respectively. Residents in Medicaid-intense zip codes were 59% nonwhite versus 31% nonwhite in the nation as a whole.

Nonwhite residents are much more likely than white residents to live in a zip code where Medicaid prescribing rules will affect their physician. Any legislation-induced changes in prescribing patterns seem likely to disproportionately impact both Medicaid and non-Medicaid minority residents in these areas.