Risk factors for hospitalization and surgery in patients with rheumatoid arthritis: implications for capitated medical payment.

Risk factors for hospitalization in patients with rheumatoid arthritis were analyzed to determine if factors proposed for use in adjusting Medicare capitation payments to prepaid health plans are, in fact, associated with use of costly medical care for this illness. Participating physicians from a random sample of half the rheumatologists in northern California provided us with the names of all patients with rheumatoid arthritis presenting during a 1-month period. We surveyed 754 (89%) of these patients in both 1982-83 and 1984 to obtain information about health care use in the previous 12 months. We found that baseline functional status and prior-year admissions (proposed Medicare adjustment factors), as well as disease-specific severity measures, predicted subsequent admissions. The association of prior with subsequent admissions was independent of disease severity and physician characteristics. Adjusting capitation payments for both health status and prior use will increase incentives for prepaid health plans to enroll patients with rheumatoid arthritis who have high expected medical costs.