Correlation of serum IgA rheumatoid factor levels with disease severity in rheumatoid arthritis.

In the present study, the IgA rheumatoid factor (IgA RF) was assayed by ELISA in 114 sera of patients with active RA. IgA RF was found in the sera of 38 (33.3%) patients. A total of 56 disease variables were studied, differences in variables between IgA RF positive and negative patients were analyzed. The presence of IgA RF was found to be associated with a rapid progressive course, RA activity, onset of extra-articular manifestations (especially systemic rheumatoid vasculitis), high IgM RF titres, circulating immune complexes, cryoglobulins, and C-reactive protein levels. There was no statistically significant difference in serum IgA levels between IgA RF seropositive and seronegative patients. The presence of IgA RF showed a positive correlation with the level of IgM RF. The results of this study showed that the determination of IgA RF has a practical use in the establishment of the severe course of RA with systemic damages.