Rheumatoid factor positivity in antineutrophil cytoplasmic antibody-associated vasculitis: a distinct clinical entity or innocent bystander?

Objective To investigate the significance of RF positivity in ANCA-associated vasculitis (AAV) patients. Methods AAV patients were divided into groups as follows: RF (+)/ANCA (+) (n  = 94), RF (−)/ANCA (+) (n  = 80), RF (+)/ANCA (−) (n  = 15) and RF (−)/ANCA (−) (n  = 25). Their clinical data, organ involvement patterns, laboratory data, and patient outcomes were assessed. Kaplan–Meier analysis and propensity score matching (PSM) were performed to compare outcomes and analyse differences between the groups. Results Of the 214 patients, RF and ANCA positivity was found in 109 (50.9%) and 174 (81.3%) patients, respectively. RF (+)/ANCA (+) patients more frequently presented with general manifestations (58.5%) than the other groups. Additionally, compared with those of RF (−)/ANCA (+) group, RF (+)/ANCA (+) patients were older, had higher white blood cell, neutrophil, platelet counts and acute phase reactants; however, creatinine and albumin levels were lower. The end-stage kidney disease-free survival rate was significantly higher in the RF (+)/ANCA (+) group (P  =0.013), while the proportion of renal involvement was comparable to the RF (−)/ANCA (+) group. PSM showed no difference in patient outcomes between the two groups after adjustment. Conclusion RF positivity was associated with a distinct phenotype in AAV patients. In particular, difference was observed in clinical features and outcomes between RF (+)/ANCA (+) and RF (−)/ANCA (+) groups, although the direct prognostic implication of RF was not evident. [ABSTRACT FROM AUTHOR]