Primary care is the principal setting in which adults receive routine preventive care such as influenza vaccinations and pap smears. Several studies identify a positive association between density of primary care providers (PCPs), greater receipt of preventive care, and better adult health outcomes within counties in the United States (Macinko et al. 2007). Although important, these studies do not allow us to consider how provider supply might differentially influence access to care for different subgroups of patients. For example, patients that have established care may be less influenced by PCP supply than patients that do not regularly visit a provider. The Affordable Care Act will dramatically increase the number of newly insured adults, which is projected to intensify demand for providers in certain regions (Huang & Finegold 2013).

We examined how availability of primary care appointments for new patients explains variation in utilization of preventive care for different subgroups of adults. We measured appointment availability using data from an experimental audit study. Field staff, posing as prospective patients, recently called 13,602 primary care practices in 10 politically and geographically diverse states. The calls followed a standardized script, except that the reason for the visit and the patient’s insurance status (Medicaid, private, uninsured) were experimentally manipulated. Using the audit study data, we calculated a county-averaged probability of receiving a visit for adults overall, and for different insurance subgroups. County-level measures were linked to individual-level data from the 2010 Behavioral Risk Factor Surveillance System (BRFSS). BRFSS collects data on physical exams, pap smears, mammograms, prostate exams, colonoscopies and influenza vaccinations. BRFSS releases county identifiers for the most populous counties in the United States. For our 10 states, BRFSS identifies 69 counties covering 37,346 non-elderly adults.

Although we expected that utilization of preventive care for both insured and uninsured adults would be greater in counties with higher new appointment availability, we found that the association was generally negative. In regression analysis, we found negative associations tended to be larger for uninsured than for insured populations. For example, controlling for individual-level characteristics, a 10 percentage point increase in the county-level appointment availability rate was associated with a 3 point decrease in the flu immunization rate for uninsured individuals, and a 1.1 point decrease for insured individuals. One exception was that higher county-level appointment availability was associated with greater visits for check-ups for uninsured adults (but not for those with private insurance).

Finally, we explored whether use of preventive care might be more responsive to the difference in appointment availability for privately-insured and Medicaid/uninsured callers, rather than the average across groups. We consistently found that use of preventive care was higher in counties with smaller gaps in availability between the two groups of callers. The effect was largest for uninsured adults. Taken together, our findings suggest that areas with lower appointment availability tend to be places where access is better overall (perhaps more patients already have established care and new visits are less frequently demanded), but unequal access environments are especially detrimental for the uninsured.