Insurance, income, and access to ambulatory care in King County, Washington.

OBJECTIVES: We studied simultaneous effects of income and insurance on access measures in an indigent population, focusing on Medicaid and the marginal effects of increasing income.
METHODS: Surveys were distributed in waiting rooms of county clinics and welfare offices. Models examined insurance (private, Medicaid, or none), income (to twice the poverty level), single-parent status, age, gender, and presence of a regular source of care; first-order interactions were evaluated.
RESULTS: In terms of ease of access, postponing care, and having a regular source of care, uninsured respondents fared worst and Medicaid recipients were at an intermediate level. However, relative to those with private insurance, Medicaid recipients had four times the odds, and uninsured respondents twice the odds of being denied care. Income had no consistent effect; however, older, poorer people may have greater problems. For preventive services, income was significant, while differences between Medicaid and private insurance were generally not significant.
CONCLUSIONS: Except for denial of care, access for indigent people is improved by Medicaid but remains worse than the access of those with private insurance. Income had variable effects, but support for income criteria used for public insurance eligibility was not found.