Utilization and Cost of the Biologic Disease Modifying Anti-rheumatic Drugs among Medicare Beneficiaries with Rheumatoid Arthritis

Abstract

Background: Disease modifying anti-rheumatic drugs (DMARDs) are essential for symptom control among rheumatoid arthritis (RA) patients. Biologic DMARDs are expensive and typically used among moderate to severe RA patients. The prevalence of RA is higher among Medicare beneficiaries compared to the rest of the population in the U.S (2% vs. 0.6%). The coverage rules of Medicare, in addition to access factors and patient preferences, may influence the use of facility-administered, infusible biologics (Part B covered) and home-administered self-injectable/oral biologics (Part D covered). However, there is limited information about utilization patterns of biologic DMARDs by route of administration and their impact on Medicare spending overall. The goals of this dissertation were to identify patient factors and healthcare expenditure associated with biologic DMARD use by route of administration among Medicare beneficiaries with RA. Methods: The study population consisted of Medicare beneficiaries with RA from the 5% random sample of the Chronic Conditions Warehouse database from 2006-2015. First, the study analyzed patient-level factors associated with biologic DMARD use by route of administration using generalized estimating equations. Second, adherence (PDC>80%), discontinuation, and switching patterns for biologic DMARDs were measured, accounting for patient level-factors , using logistic regression, Cox proportional hazards models, and chi-square analyses, respectively. Third, the study compared annualized average healthcare costs of patients who were adherent to versus non-adherent to biologic DMARDs. Results: Among Medicare beneficiaries diagnosed with RA who received DMARD treatment (n=46,002), 71.8% (n=33,028) used traditional DMARDs, and among biologic DMARD users (n=12,931), twice as many used infusible biologics (18.3%, n=8,436) compared to self-injectable/oral (9.9%, n=4,538). Beneficiaries who were low-income subsidy (LIS) recipients i.e. who had lower out-of-pocket costs for using biologics, (compared to non-LIS) had 4.54 times higher odds of using self-injectable/oral biologics (95% CI: 4.2 - 5.0) and 5% lower odds of discontinuing biologic DMARDs (OR=0.94, 95% CI: 0.91-0.97). The total healthcare cost was lower among adherent compared to non-adherent infusible biologic DMARD users ($33,797 vs. $90,181; p<0.001) and among adherent vs. non-adherent self-injectable/oral biologic DMARD users ($64,977 vs. $80.908; p<0.05). Conclusions: Adherence and cost savings generated, as a result, varied by the biologic DMARD route of administration. Additionally, beneficiaries' LIS status was associated with the route of administration used and the discontinuation rates, indicating an association with their out-of-pocket costs. These findings are relevant to the discussion about the proposed transition of Part B covered infusible medications under the Part D which is projected to increase the beneficiary out-of-pocket cost. The evidence on adherence can also be used for value-based insurance design involving RA biologics. Future research could leverage the findings from this study to additionally explore how biosimilar products may impact overall biologic utilization and RA treatment spending.