Rheumatoid factor is correlated with disease activity and inflammatory markers in antineutrophil cytoplasmic antibody-associated vasculitis

Background Some patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) also have positivity of rheumatoid factor (RF). However, the clinical significance of this occurrence remains unknown in AAV patients. The aim of this study was to clarify an association between the presence of RF and clinical features in patients with AAV. Results Forty-seven patients diagnosed with AAV who were not complicated with RA were enrolled in this study. We compared clinical manifestations of AAV between an RF-positive subset (n = 29) and an RF-negative subset (n = 18). The Birmingham Vasculitis Activity Score (BVAS) was higher (P = 0.026) in the RF-positive subset than in the RF-negative subset. The levels of CRP and ESR were higher in the RF-positive patients (P = 0.020 and P = 0.007, respectively) compared to the RF-negative subset. IgM-RF titers were significantly correlated with the BVAS (r = 0.50, P = 0.0004). In addition, the IgM-RF titers had significant correlations with the levels of CRP (r = 0.41, P = 0.004), ESR (r = 0.39, P = 0.016), IgM (r = 0.36, P = 0.016) and IgG (r = 0.37, P = 0.015). The frequency of commencement of dialysis therapy, usage of mechanical ventilation and mortality were higher in the RF-positive subset than in the RF-negative subset. Conclusions In patients with AAV, RF titers were significantly correlated with disease activity and the levels of inflammatory markers. The presence of RF could be a poor prognostic factor in patients with AAV.