The presence of
IgA-RF was determined by a sandwich-type ELISA with an antibody against the human
IgA used to capture the
immunoglobulin. Associated RF activity was revealed with a
peroxidase-conjugated human
IgG Fc fragment. Forty-nine RA patients were studied, of whom 19 had an increase in
IgA-RF (38%). The control group comprised 30 RA patients without
IgA-RF.
RESULTS: None of the patients had isolated
IgA-RF. In the selected 19 RA patients, the OD of
IgA-RF (0.971 +/- 0.62 U) was higher than the
IgM-RF (mean OD: 0.675 +/- 0.522 U). A statistically significant correlation was found between
IgA-RF and
IgM-RF (r = 0.64, p < 0.0001). No correlation was noted between the
IgA concentration and the
IgA-RF titer. The two groups were comparable for age, disease duration, sex ratio and previous
DMARD use. We observed that patients with RA associated with increased
IgA-RF more often had the
sicca syndrome, but no other extra-articular features. RA patients with
IgA RF also had more erosive disease: the mean Larsen score at the hand and wrist was 76 (SD = 68) versus 54 (SD = 60) in the controls, p < 0.02. Replacement surgery for the hip or knee was necessary in 47% of the RA patients with
IgA-RF, versus 13% in the controls, p < 0.01. No association of
IgA-RF with disease activity was noted.
CONCLUSION: