Background The simplified disease activity index (SDAI) 50 has good agreement with the EULAR response measures for early rheumatoid arthritis (RA). Although there are reports on early RA, there have been no reports on long-established RA.

Objectives In this study, we analyzed the relationships between various baseline factors and SDAI 50 after six months of biological disease-modifying antirheumatic drugs (bDMARDs) treatment to determine the prognostic factors for long-established RA.

Methods The subjects were 332 RA patients who had been treated with bDMARDs for 6 months. The following characteristics were investigated: age, gender, disease duration, smoking history, body mass index, steroid and methotrexate dosage, previous bDMARDs use, combined csDMARDs use, ESR, CRP, serum matrix metalloproteinase-3 levels, SDAI score, health assessment questionnaire disability index score (for daily living activities) and short form-36 score (for quality of life). As a primary outcome index, SDAI response was defined as a 50% reduction in SDAI score between baseline and 6 months (SDAI 50).

Results The group of RA patients who achieved SDAI 50 (Group A: 204 patients) had a higher tender joint count (p=0.041), swollen joint count (p=0.001), evaluator's global assessment (p=0.027) and SDAI (p=0.006) than did those who did not achieve SDAI 50 (Group B: 152 patients). Before the start of the treatment, steroid dosage (p=0.0187, odds ratio: 1.119, 95% CI: 1.029–1.229) and SDAI (p=0.0003, odds ratio: 0.953, 95% CI: 0.928–0.978) were determined based on logistic regression analysis. Comparisons were performed between Groups A and B and between before treatment and after 6 months of SDAI. Group A showed a significant improvement compared to Group B by repeated measure analysis of variance (ANOVA) (Interaction: p=0.000, Group A vs. Group B: p=0.000, before vs. after treatment: p=0.000).

Conclusions Our study demonstrated that RA patients with a lower steroid dosage and higher SDAI baseline are more likely to achieve SDAI 50 with bDMARD treatment.

Acknowledgements ASHURA Resistry Groups

Disclosure of Interest Y. Miwa Grant/research support from: Astellas Pharma Inc., Mitsubishi Tanabe Pharma Corporation, AbbVie CK, Pfizer Japan Inc., Chugai Pharmaceutical Co., Ltd., Eizai Co., Ltd, Asahi Kasei Pharm Co., Ltd, YL biologics Ltd., Japan Blood Products Organization,. Ono Pharmaceutical Co., Ltd., Nippon Kayaku Co., Ltd., and Teijin Pharma Ltd., A. Nishimi: None declared, S. Nishimi: None declared, T. Tokunaga: None declared, S. Ishii: None declared, T. Kasama Grant/research support from: Mitsubishi Tanabe Pharma Corporation and AbbVie CK.