IgA rheumatoid factor in primary Sjogren's syndrome

To assess the serum level of immunoglobulin A rheumatoid factor (IgA-RF) in patients with primary Sjogren's syndrome (pSS) and study the association with immunological and clinical factors.

Sera from 97 pSS patients diagnosed according to the preliminary European criteria and 100 controls were analysed for IgA-RF in a cross-sectional study design.

IgA-RF was detected in serum of 25.8% of the pSS patients and in 1% of the controls. In patients with positive vs. negative IgA-RF, the focus scores in biopsy of the minor salivary glands were 4.41 and 1.43 (p<0.0001), respectively. There was a correlation between positive IgA-RF and positive antinuclear antibodies (ANA) (r = 0.263, p<0.009), IgM-RF (r = 0.70, p<0.0001), anti-SSA/SSB (r = 0.73, p<0.0001), and a high serum level of IgG (r = 0.59, p<0.0001). The presence of renal disease was higher in IgA-RF-positive vs. negative pSS patients (20.0% vs. 5.6%, p = 0.047). The serum level of the hormone prolactin (PRL) correlated to the serum level of IgA-RF (r = 0.31, p = 0.026).

The presence of IgA-RF in patients with pSS is closely associated with the presence of autoantibodies, and with focus scoring in biopsies of the salivary glands. IgA-RF is associated with renal disease in pSS but we found no correlation to other extraglandular manifestations.