title: Anti-cyclic citrullinated peptide antibodies and rheumatoid factor in Sjögren's syndrome.
abstract: OBJECTIVE
  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).
  
  
  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.
authors.affiliation: Portuguese Institute of Rheumatology, Lisbon, Portugal. fduartebarcelos@gmail.com
authors.forename: Filipe
authors.initials: F
authors.lastname: Barcelos
authors.forename: Isabel
authors.initials: I
authors.lastname: Abreu
authors.forename: José Vaz
authors.initials: JV
authors.lastname: Patto
authors.forename: Hélder
authors.initials: H
authors.lastname: Trindade
authors.forename: Ana
authors.initials: A
authors.lastname: Teixeira
mesh_terms: D001323:Autoantibodies / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D012189:Retrospective Studies; D012217:Rheumatoid Factor / Q000097:blood*; D012859:Sjogren's Syndrome / Q000097:blood* / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor