PRTN3 and rheumatoid arthritis: Hence, in the present study we have investigated the associations of EBV, B19 and CMV viruses with ACPA-positive and ACPA-negative disease, in relation to SE, smoking status, disease activity score in 28 joints (DAS28) and C-reactive protein (CRP) levels by measuring anti-viral IgG in sera from 990 patients with RA (cases) and 700 matched controls.