Objectives: To identify predictive factors for remission by tocilizumab monotherapy in rheumatoid arthritis (RA) patients. Methods: This is a post hoc analysis of the SURPRISE study, a 2-year randomized, controlled study comparing the efficacy of tocilizumab with (ADD-ON) and without methotrexate (SWITCH). The primary endpoint was DAS28-ESR remission (<2.6) at week 24. The change in modified total Sharp score from baseline to week 52 (ΔmTSS/year) was also assessed as an endpoint. The effect of clinical parameters at baseline on remission was estimated by logistic regression analysis. Results: In SWITCH (n = 96), CRP, SAA, RF, and DAS28 at baseline showed predictive value for DAS28 remission in unadjusted analysis. Adjusted analysis confirmed SAA and DAS28 as predictive factors, with SAA having the highest value (ROC-AUC = 0.731). Furthermore, structural remission (ΔmTSS/year ≤ 0.5) rate was significantly higher in patients with SAA of < 50.0 μg/mL than other patients. In contrast, in ADD-ON (n = 98), only DAS28 showed predictive value for DAS28 remission. In patients with SAA < 50.0 μg/mL, both DAS28 remission and structural remission rate were comparable between SWITCH and ADD-ON. Conclusion: RA patients with low SAA levels at baseline may benefit similarly from tocilizumab with and without methotrexate. Trial registration number: NCT01120366.
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