Clinical outcomes in psoriatic arthritis patients with rheumatoid factor positivity

OBJECTIVES: The clinical and immunologic significance of rheumatoid factors (RF) in psoriatic arthritis (PsA) remains unclear. We aimed to determine the frequency and impact of RF positivity on clinical outcomes and biologic (b) disease-modifying anti-rheumatic drug (DMARD) discontinuation in PsA. METHODS: Patients enrolled after 1996 from a large PsA cohort were included for this study. RF was tested annually and was defined as ever positive or newly positive (excluding those positive at enrolment). Associations of RF with clinical outcomes, including achievement of minimal disease activity (MDA), components of MDA and bDMARD discontinuation, were assessed using univariable (UV) and multivariable (MV) generalized estimating equations. RESULTS: Among 1074 patients, RF positivity was observed in 173 (16.1%) overall, including 55 (5.1%) who were positive at baseline. RF positivity was significantly associated with reduced odds for achievement of MDA (MV, OR 0.53, 95% CI 0.37-0.77), driven by worse patient pain, patient global and physical function, particularly in the bDMARD subgroup. These associations persisted in the bDMARDs subgroup when analyses were restricted to new RF positivity. Additionally, ever and new RF positivity was associated with increased odds for bDMARD discontinuation (MV, OR 2.65, 95% CI 1.34-5.24 and 2.78, 95% CI 1.57-4.92, respectively) independent of joint and skin disease activity. CONCLUSION: RF was observed in 16.1% of the cohort, with 5.1% being positive at baseline. RF positivity was associated with lower odds for achievement of MDA and with bDMARD discontinuation.