Prevalence of IgA class antibodies to cyclic citrullinated peptide (anti-CCP) in patients with primary Sjögren's syndrome, and its association to clinical manifestations.

This study aims to determine the prevalence and clinical significance of anti-CCP isotype IgA in a population of patients with primary Sjögren's syndrome (pSS). Sixty-two patients diagnosed according to the USA-European classification criteria for pSS were examined two to four times during a 60.4-month follow-up, and clinical and laboratory data were registered prospectively. Antibodies against cyclic citrullinated peptides (anti-CCP) isotype IgG and IgA were determined in serum samples by an immunofluorescence ELiA™ system. Healthy individuals and patients with rheumatoid arthritis (RA) with matching sex and age served as controls. The serum level of anti-CCP IgA was higher in pSS patients than healthy individuals (2.37 versus 1.37 EU/ml; p < 0.0001), and lower than matching patients with RA (2.37 versus 6.51 EU/ml; p < 0.0001). Using a cutoff for anti-CCP IgA at 4.12 EU/ml, 8.1 % pSS patients had a positive test compared to 26.7% of patients with RA. Positive test for anti-CCP IgG was demonstrated in 4.8% pSS patients. There were no significant differences between demographic and serological variables in pSS patients with positive versus negative anti-CCP IgA. There was significantly more pSS patients with cutaneous vasculitis in the anti-CCP IgA-positive population, however (40.0% versus 3.5%; p = 0.030), and there was a nonsignificant trend of lower unstimulated whole saliva collection (USWC) in the anti-CCP IgA-positive patients. There were no correlations between arthritis and anti-CCP IgG and IgA. This is the first study on the prevalence of anti-CCP isotype IgA in patients with pSS, demonstrating that anti-CCP isotype IgA is moderately increased in patients with pSS but lower than the prevalence in patients with RA. The presence of IgA and IgG anti-CCP isotypes were not associated with arthritis or other clinical manifestations in pSS patients. We demonstrated an association of anti-CCP IgA to cutaneous vasculitis.