Differences in resource use and costs of primary care in a large HMO according to physician specialty

Objective. To determine if primary care physician specialty is associated w ith differences in use of health services. Data Sources. Automated outpatient diagnostic, utilization, and cost data o n 15,223 members (35-85 years of age) of a large group model HMO. Study Design. One-year prospective comparison of primary care provided by 2 45 general internists (GIMs), 60 family physicians (FPs), and 55 subspecial ty internists (SIMs) with case-mix assessed during a nine-month baseline pe riod using Ambulatory Diagnostic Groups. Principal Findings. Adjusting for demographics and case mix, patients of GI Ms and FPs had similar hospitalization and ambulatory visit rates, and simi lar laboratory and radiology costs. Patients of FPs made fewer visits to de rmatology, psychiatry, and gynecology (combined visit rate ratio: 0.86, 95% CI: 0.74-0.96). However, they made more urgent care visits (rate ratio 1.1 9, 95% CI: 1.07-1.23). Patients of SIMs had higher hospitalization rates th an those of GIMs (rate ratio 1.33, 95% CI: 1.06-1.68), greater use of urgen t care (rate ratio: 1.14, 95% CI: 1.04-1.25), and higher costs for pharmacy (cost ratio: 1.17, 95% CI: 0.93-1.18) and radiologic services (cost ratio: 1.14, 95% CI: 1.01-1.30). The hospitalization difference was due partly to the inclusion of patients with specialty-related diagnoses in panels of SI Ms. Radiology and pharmacy differences persisted after excluding these pati ents. Conclusions. In this uniform practice environment, specialty differences in primary care practice were small. Subspecialists used slightly more resour ces than generalists. The broader practice style of FPs may have created ac cess problems for their patients.