Adherence with bisphosphonate therapy in US veterans with rheumatoid arthritis

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Pharmacy Benefits Management program data for patients enrolled in the Veterans Affairs Rheumatoid Arthritis (VARA) registry were linked with clinical data to determine bisphosphonate adherence and persistence among US veterans with rheumatoid arthritis (RA) and to determine factors associated with adherence. The primary outcome measures were the duration of bisphosphonate therapy and the medication possession ratio (MPR). Patients with an MPR <0.80 were classified as nonadherent. Potential covariates considered in the analysis included patient demographics, RA disease activity and severity parameters, and factors associated with osteoporosis risk. Associations of patient factors with duration of therapy and adherence were examined using multivariable regression modeling. Bisphosphonates were prescribed to 573 (41.5%) of 1,382 VARA subjects. The mean ± SD duration of therapy for bisphosphonates was 39.2 ± 31.4 months. A longer duration of therapy correlated with older age, more years of education, and dual x-ray absorptiometry testing. The mean ± SD MPR of VARA subjects for bisphosphonate therapy was 0.69 ± 0.28; 302 (52.7%) were nonadherent. In multivariate analyses, nonadherence with bisphosphonate therapy was associated with a longer duration of RA disease (odds ratio [OR] 1.02, 95% confidence interval [95% CI] 1.00-1.04) and duration of bisphosphonate therapy >32 months (OR 1.63, 95% CI 1.04-2.57). Whites were less likely to have a low MPR compared with nonwhites (OR 0.52, 95% CI 0.30-0.88). Nonadherence with bisphosphonates was common in this cohort of RA patients and was associated with nonwhite ethnicity, a longer duration of RA disease, and a greater duration of bisphosphonate therapy.