Clinical predictors of inadequate response to conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) including methotrexate (MTX) in untreated rheumatoid arthritis patients -A single-center observational study.

Objectives: To investigate predictors of inadequate response to first conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) including methotrexate (MTX) in untreated rheumatoid arthritis (RA) patients in daily clinical practice. Methods: Inadequate response to MTX or other csDMARDs was defined as being not low disease activity at 12 months in more than 3 of 4 composite measures, and discontinuation or start of biologic DMARDs. The association between baseline factors and csDMARDs-IR was assessed by univariate and multivariate logistic regression analyses. Results: Four hundred and eleven and 146 patients were started on MTX and other csDMARDs, respectively; 218 patients were responsive to MTX, with a response rate of 47.0%. Tender joint count (TJC, >= 6 in 28joints, odds ratio [OR] = 1.67, 95% confidence interval [CI] 1.06-2.64) and CRP (>= 1.0 mg/dL, OR = 1.72, 95%CI: 1.10-2.70) at baseline were identified as predictors on multivariate logistic regression analysis. TJC (OR = 3.60, 95%CI: 1.29-10.00) was the factor identified as a predictor of the development of other csDMARDs-IR. Conclusion: In this observational study, patients with untreated RA at risk of inadequate response to MTX included those with a higher TJC and higher CRP, while a higher TJC was the only independent predictor of an inadequate response to csDMARDs other than MTX.