Medicare coverage of tumor necrosis factor alpha inhibitors as an influence on physicians' prescribing behavior

Rheumatoid arthritis is a chronic debilitating disease that affects 1% of the population. Tumor necrosis factor alpha inhibitors, such as etanercept and infliximab, have revolutionized the treatment of rheumatoid arthritis by averting disability but at great financial expense, generally borne by third-party payors. Prior to implementation of the Medicare Modernization Act, Medicare reimbursed for the infusion drug infliximab but not for the self-injectable drug etanercept. To determine the impact of this differential Medicare drug coverage on physicians' prescribing behavior in clinical practice, we analyzed patterns of prescribing etanercept and infliximab for patients with rheumatoid arthritis who had public insurance compared with those who had private insurance.

We conducted an observational cohort study of 1663 patients with rheumatoid arthritis newly prescribed etanercept or infliximab after enrollment in the National Databank for Rheumatic Diseases. Univariate and multivariable analyses of patient demographic and disease characteristics were conducted to characterize predictors of the biologic drug prescribed.

Treatment groups who received etanercept and infliximab differed in 6 of 8 demographic variables and in 8 of 10 disease variables. However, stratification by type of insurance reduced many of these differences. In multivariable analyses, type of insurance plan and demographic factors were strong predictors of differential prescribing of etanercept compared with prescribing of infliximab, whereas disease characteristics generally were not. Patients with public insurance were 30% more likely to receive infliximab than those who were privately insured (P<.001).

Public insurance predicted prescription of infliximab, reflecting preferential Medicare reimbursement for infusion drugs. Financial considerations are influential in physicians' prescription decisions. Differential drug coverage has an impact on patient care and health care costs because it influences physicians' prescribing behavior.