Anti-cyclic citrullinated peptide antibodies and rheumatoid factor in Sjögren's syndrome.

OBJECTIVES: The purpose of this study was to evaluate the prevalence and clinical significance of anti-cyclic citrullinated peptide antibodies (anti-CCP-Abs), IgM and IgA rheumatoid factors (RFs) in primary Sjögren's Syndrome (pSS).
MATERIALS AND METHODS: We compared clinical and serological characteristics of 31 pSS and 31 Rheumatoid Arthritis (RA) patients. Both, anti-CCP-Abs and RFs (IgM, IgA) directed against Fc determinants of IgG from humans and rabbit were detected by enzyme-linked immunosorbent assay (ELISA). We included 31 blood donors as control group for the evaluation of RFs and anti-CCP-Abs. Nine (29%) pSS patients presented arthritis, and 10 (32,3%) RA patients also had secondary Sjögren's syndrome (sSS)
RESULTS: IgM and IgA RFs prevalence was similar in pSS and RA, whichever the antigene (Human or Rabbit IgG) used. However, RA patients with sSS showed a tendency to present more often RF positivity, longer disease duration and higher ESR and CRP when compared with pSS patients with arthritis. Anti-CCP-Abs were detected in 64,5% of RA patients and in only 6,9% of pSS patients (p<0,0005). Anti-CCP-Abs were more often positive in RA patients with sSS (RA/sSS) (8 patients, 80%) than in RA patients without sSS (18 patients, 58,1%), and were absent in pSS patients with arthritis. RF-positive pSS patients presented more often pulmonary involvement and higher inflammatory parameters, and less often neuropathy compared to RF-negative patients. In controls, anti-CCP-Abs were absent and RFs were negligible.
CONCLUSIONS: Anti-CCP-Abs were detected in only a few pSS patients, none of whom presented arthritis, which contrasts with the high frequency of these antibodies in RA/sSS. These results suggest that anti-CCP-Abs could be useful in the distinction between pSS and RA with sSS. Although not useful for the differential diagnosis between RA and pSS, RFs may have a prognostic role in pSS.