PMS45 - Adherence to Biologic and Conventional Disease Modifying Anti-Rheumatic Drugs in Patients with Rheumatoid Arthritis

Abstract

Though biologic disease modifying anti-rheumatic drugs (bDMARDs) have shown higher efficacy and better tolerance in clinical trials than conventional disease modifying anti-rheumatic drugs (cDMARDs), their cost could potentially affect patient adherence. The objective of this study was to estimate adherence to bDMARDs and cDMARDs in patients with Rheumatoid Arthritis (RA), and to assess if adherence is associated with DMARD type (bDMARDs vs cDMARDs) or patient out-of-pocket (OOP) costs. Patients with RA from the 2008-2012 Medicare Current Beneficiary Survey (MCBS) data with at least 2 Medicare Part D claims for DMARDs were included. Medication adherence was calculated as proportion of days covered (PDC) in six-month period following date of first DMARD fill. Individuals with PDC>=0.80 were considered adherent. Total OOP medication costs per patient were generated as a sum of OOP costs per claim. Logistic regression was used to assess associations between adherence and DMARD type and OOP costs. 542 patients met inclusion criteria. 85% were on cDMARDs. The proportion (95% confidence interval) of patients adherent to bDMARDs, 0.48, (0.40, 0.56), did not differ significantly from that for cDMARDs, 0.52, (0.47. 0.56) (p=0.1293). Patients on bDMARDs had significantly higher mean OOP costs ($922.86±1720) than patients on cDMARDs ($40.26±51.93). In univariate logistic regressions, there was no significant association between DMARD type (p=0.13) and adherence, or OOP costs (p=0.72) and adherence. In multivariate logistic regression, patients on bDMARDs’ estimated odds (O.R.=0.6, 95% C.I.(0.351, 1.032)) of being adherent compared to patients on cDMARDs, after controlling for age, gender, education and OOP costs, was not significant (p=0.06). Adherence to DMARD therapy in patients with RA was relatively low at approximately one-half, and did not differ significantly between patients on biologic DMARDs (0.48±0.08) and those on conventional DMARDs (0.52±0.04), although patients on bDMARDs paid more out-of-pocket on an average as compared to patients on cDMARDs.