Abstract
Medication adherence is believed to be a major contributor to treatment outcomes yet studies quantifying this relationship as rare in rheumatoid arthritis (RA). To determine the association of adherence to DMARD therapy with treatment outcomes among new and existing DMARD users over 2 years. Relevant clinical parameters were obtained from a longitudinal cohort of RA patients, most of who were treated with combination therapy. Patients were classified as adherent if the proportion of days covered for each DMARD was ≥80%. Outcome measures were the change in the disease activity score in 28 joints (DAS28), simplified disease activity index (SDAI), modified health assessment questionnaires (mHAQ) and proportion of patients who achieved response criteria. An inverse propensity-score weighting method was used to estimate the association of adherence with each outcome. Of 194 patients invited, a total of 111 patients (new = 45 and existing = 66 DMARD users) met study eligibility. DMARD-naive patients demonstrated relatively higher rates of adherence compared to existing users. After controlling for confounding variables, adherence was significantly associated with reduction in DAS28 (β = −1.5, 95% CI of β = − 2.17 to −0.83, p < 0.0001), SDAI (β = −9.44, 95% CI of β = −15.53 to −3.35, p = 0.002) and mHAQ (β = −0.269, 95% CI of β, −0.462 to −0.077, p = 0.017) over 2 years among new patients and adherent patients were more likely to achieve most response criteria compared to non-adherent patients. Such associations were not replicated among existing DMARD users. Adherence to combination DMARD therapy was associated with improvements in disease activity and functional outcomes in the first 2 years of therapy.
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Acknowledgements
The authors are grateful to all rheumatologists and rheumatology nurses involved in the treatment and care of patients as well as patients who participated in this study.
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The authors had no financial support or other benefits from commercial sources for the work reported in the manuscript, or any other financial interests that could create a potential conflict of interest or the appearance of a conflict of interest with regard to the work.
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The authors have no competing interests to report.
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Ethics approval was obtained from the University of South Australia (protocol no.0000031928) and the Royal Adelaide Hospital (protocol no.140303) for the longitudinal observational cohort and for the linkage of prescribing data.
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296_2017_3655_MOESM3_ESM.tif
The rate of medication adherence according to different definitions of adherence:*P<0.05 for DMARD-naïve vs experienced patients; PDC, proportion of days covered; PDC-1, adherence of ≥80% with at least one DMARD; PDC-average, average PDC≥80%; PDC-all, PDC≥80% for all DMARDs (TIF 168 KB)
296_2017_3655_MOESM4_ESM.tif
Proportion of patients who achieved EULAR and SDAI response criteria and MCID for mHAQ stratified according to treatment status:*P<0.0001 for DMARD-naïve vs experienced patients; EULAR, European League Against Rheumatism; SDAI, Simplified disease activity index; MCID, minimally clinically important differences, mHAQ, modified health assessment questionaries (TIF 204 KB)
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Wabe, N., Lee, A., Wechalekar, M. et al. Adherence to combination DMARD therapy and treatment outcomes in rheumatoid arthritis: a longitudinal study of new and existing DMARD users. Rheumatol Int 37, 897–904 (2017). https://doi.org/10.1007/s00296-017-3655-z
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DOI: https://doi.org/10.1007/s00296-017-3655-z