Background/Purpose: Rheumatoid factors (RFs) are RA-related autoantibodies like anti-cyclic citrullinated peptide antibodies, and are used for classifying and diagnosing RA. In addition, positivity and high titers in serum RFs are risk or prognostic factors of joint damage for both early and established RA patients. However, it remains unclear whether the changes in serum RF titers are correlated with progressions of joint damage in RA. The purpose of this study is to clarify whether continuous decreases in RF titers during treatment with biological or targeted synthetic DMARD (b/tsDMARD) were associated with radiographic remission in progression of RA joint damage.

Methods: 130 RA patients were enrolled, who filled RA criteria 2010, were treated with b/tsDMARD for more than 4 months, had serum RF titers above 45 IU/ml at starting therapy (month 0), and were followed up until month 12. Serum RF titers were measured at month 0, 4 and 12 after starting b/tsDMARD therapy, and continuous RF decreases were defined as not less than 10% decreases in RF titers during both month 0-4 and 4-12. RA disease activity was assessed by DAS28-ESR at month 0, 4 and 12, and time-integrated DAS28-ESR was calculated. Joint damage was assessed by modified total Sharp score (mTSS) at month 0 and 12, and radiographic remission was defined as yearly mTSS progression below 0.5. Their medical records were reviewed retrospectively. In case of withdrawal from b/tsDMARD therapy during month 4-12 due to some causes, data upon the discontinuation of b/tsDMARD was used as that at month 12 using the last observation carried forward method. Baseline demographic, disease- and RF-related variables were included in univariate and multivariate logistic regression analysis for identifying the factors related to radiographic remission.

Results: Subjects were 102 female, were median age 61.7 years with 4.8 years of disease duration, and were treated with abatacept (n=27), JAK inhibitors (n=9), tocilizumab (n=39) and TNF inhibitors (n=55) in addition to MTX (median dose; 8 mg/week). Serum RF titers decreased from 127 IU/ml (month 0, median) to 89.5 (month 4, p=0.0022) and 84.5 (month 12, p=0.0115). DAS28-ESR improved from 3.92 (month 0, median) to 2.65 (month 4, p< 0.0001) and 2.58 (month 12, p< 0.0001). 65 of 130 subjects achieved radiographic remission in mTSS at month 12. During b/tsDMARD therapy, 46 of 130 patients showed continuous decreases in serum RF titers (CD group), and 84 cases did not (non-CD group). Compared with non-CD patients, CD had younger age of RA onset (p=0.0456), higher ratio of anti-TNF therapy (p=0.0170), lower DAS28-ESR at month 12 (p=0.0404) and higher ratio of radiographic remission in mTSS (p=0.0056). In multivariate analysis, continuous decreases in serum RF titers were associated with radiographic remission in mTTS (OR=3.7316; 95% CI:1.5427–9.5980) in addition to time-integrated DAS28-ESR.

Conclusion: Continuous decreases in serum RF titers were associated with radiographic remission of mTSS in RA patients treated with b/tsDMARD. The changes in serum RF titers may become a prognostic factor for joint damage in RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-association-between-continuous-decreases-in-serum-rf-titers-and-radiographic-remission-of-joint-damage-in-ra-patients-treated-with-biological-or-targeted-synthetic-dmards/