Background Methotrexate (MTX) is considered the preferred initial DMARD for the treatment of rheumatoid arthritis, but the preferred route of administration (oral or subcutaneous) is unclear.
Objectives To determine the comparative effectiveness of initial therapy with subcutaneous (sc) versus oral methotrexate (MTX) for patients with early rheumatoid arthritis (ERA) in routine clinical care.
Methods Patients with early inflammatory arthritis initiating methotrexate therapy were included from the Canadian Early Arthritis Cohort (CATCH), a multicenter, prospective cohort study of patients with ERA. All patients had a diagnosis of RA by 2010 criteria, symptom duration < 1 year and were MTX-naive or minimally exposed to MTX. The exposure was initial route of MTX (oral vs. sc) and the outcome was DAS-28 over the first year (3, 6, 9, 12 months). A linear generalized estimating equation (GEE) model was used to account for repeated measures within patients while adjusting for potential confounders.
Results 653 patients were included (442 oral MTX, 211 sc MTX). Patients treated with sc MTX were more likely to have erosions at baseline (35% vs. 25%, p=0.01), were less likely to receive other DMARDs (38% vs. 58%, p<0.01), and had a higher median starting dose of MTX (25 mg vs. 15 mg, p<0.01). Other characteristics were similar between groups. In the GEE model, after adjusting for all potential confounders except starting dose of MTX, sc MTX was associated with a reduction in the average DAS-28 score over the first year of 0.23 [(95%CI:0.07, 0.39), p<0.01]. After adjusting for starting dose, the route of MTX (oral/sc) was no longer significant (p=0.26), but for each additional mg of MTX, the average DAS-28 decreased by 0.02 [(95%CI:0.003, 0.04), p=0.02]. There was significant variability in the use of sc between centers.
Conclusions Initial sc MTX use was associated with lower DAS28 scores over the first year of treatment, which appears to be mediated through the higher starting dose used in clinical practice.
Acknowledgements Dr. Glen Hazlewood is supported by an Alberta Innovates Health Solutions Clinical Fellowship
Disclosure of Interest G. Hazlewood: None Declared, C. Thorne: None Declared, J. Pope: None Declared, G. Boire: None Declared, B. Haraoui: None Declared, C. Hitchon: None Declared, E. Keystone: None Declared, D. Tin: None Declared, V. Bykerk Grant/research support from: Amgen, Pfizer, Roche, BMS, UCB, Janssen Biotech and Abbott
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