Utilization of specialty and primary care: the impact of HMO insurance and patient-related factors.

Appropriate utilization of primary and specialty care has stimulated substantial debate, but the portion of the discussion focused on policies that restrict or discourage direct access to specialists has been largely uninformed by empirical analysis. Using data from the National Ambulatory Care Survey (1985 to 1992 surveys), we examined the associations of patient and physician demographics and health maintenance organization (HMO) insurance status with the utilization of primary compared with specialty care. Office visits for adult patients seen by primary care physicians and specialists were analyzed for: (1) patient-initiated utilization of specialists (patient self-referral) compared with that of primary care physicians; and (2) utilization of specialists compared with that of primary care physicians, stratified by HMO insurance status. After multivariate adjustment, patient self-referral was less likely among black patients (adjusted odds ratio [AOR] = 0.67; 95% confidence interval [CI] = 0.59 to 0.76), self-pay (AOR = 0.81; 95% CI = 0.74 to 0.88), or patients with Medicaid (AOR = 0.51; 95% CI = 0.43 to 0.61). The proportion of non-HMO patients seeing specialists remained stable (44.9%). For HMO patients, the proportion of total visits made to specialists increased from 27.6% in 1985 to 41.3% in 1991, then dropped to 33.2% in 1992. Disparities in utilization of specialists by women, blacks, and patients with Medicaid observed among non-HMO patients were not found in the HMO population. Specialists were more likely to see HMO patients for follow-up of a known problem, whereas non-HMO patients were more likely to have specialist follow-up visits for new problems. The results suggest greater utilization of specialists by male, white, and privately insured patients. The findings may partially account for disparities in specialty procedure use, and suggest that HMO insurance may reduce some of these disparities. The less frequent and more selective use of specialists among HMO patients suggests an evolving role for specialists in managed care.