Specialty Tier-Level Cost Sharing and Biologic Agent Use in the Medicare Part D Initial Coverage Period Among Beneficiaries With Rheumatoid Arthritis.

Objective: To examine associations between specialty tier-level cost sharing and use of biologic agents for rheumatoid arthritis (RA) during Medicare Part D's initial coverage period (ICP).

Methods: This was a retrospective study using 2007-2010 5% sample Medicare files to examine RA patients with use of a Part D RA biologic agent in the prior year. Patients without low-income subsidies (non-LIS group), who faced specialty tier-level cost sharing, were compared to a control group of low-income subsidy patients (LIS group), who faced nominal out-of-pocket costs in the ICP. Outcomes included use of a Part D or Part B RA biologic agent during the ICP and presence of a ≥30-day continuous gap in treatment among Part D biologic agent users in the ICP. Risk-adjusted outcomes were estimated using logistic regressions, controlling for patient demographic, clinical, and Part D plan characteristics.

Results: On average, a 30-day Part D biologic agent supply cost the non-LIS group $484 out of pocket (29.9% cost sharing) versus $5 (0.3% cost sharing) for the LIS group. The non-LIS group was less likely to fill Part D biologic agents (61.2% versus 72.7%, odds ratio [OR] 0.58 [95% confidence interval (95% CI) 0.46-0.72]; P < 0.001), more than twice as likely to receive Part B biologic agents (9.9% versus 4.4%, OR 2.41 [95% CI 1.61-3.60]; P < 0.001), and less likely to use any biologic agent (70.1% versus 76.9%, OR 0.69 [95% CI 0.55-0.88]; P = 0.002). The non-LIS subgroup filling Part D biologic agents had approximately twice the odds of a gap in both Part D biologic agent and any biologic agent availability.

Conclusion: Specialty tier-level cost sharing was associated with interruptions in RA biologic agent treatment among Medicare patients.