PRTN3 and rheumatoid arthritis: In particular, RA patients with established disease (cohort 2) were more likely IgM and IgA-RF positive (73.7% and 68.4%, respectively) than early RA (cohort 1) (IgM-RF: 40.0%, p = 0.05; IgA-RF: 20.0%, p = 0.01) but comparable in terms of ACPA positivity.