Prevalence of IgA class antibodies to cyclic citrullinated peptide (anti-CCP) in patients with primary Sjِgren'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 Sjِgren'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 ELiATM 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 IgApositive 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