title: The clinical and genetic associations of anti-cyclic citrullinated peptide antibodies in psoriatic arthritis.
abstract: OBJECTIVE
  Antibodies recognizing a cyclic citrullinated peptide (anti-CCP) are highly specific for rheumatoid arthritis (RA) but their role in psoriatic arthritis (PsA) remains unclear. The aim of this study was therefore to investigate the prevalence of anti-CCP antibodies in PsA and assess their clinical and genetic associations.
  
  
  METHODS
  One hundred and twenty-six patients with PsA, 40 patients with seropositive RA and 40 controls were tested for the presence of anti-CCP antibodies, rheumatoid factor (RF) and the HLA-DRB1 shared epitope. Clinical and radiological data were collected prospectively on all patients and compared between anti-CCP-positive and -negative patients.
  
  
  RESULTS
  Seven (5.6%) patients with PsA were positive for anti-CCP antibodies compared with 0% of controls and 97% of patients with seropositive RA. The presence of anti-CCP antibodies in PsA was significantly associated with the HLA-DRB1 shared epitope (P<0.005), erosive disease (P<0.05), number of swollen joints (P<0.02) and DMARD use (P<0.05).
  
  
  CONCLUSIONS
  Overall, the increased prevalence of anti-CCP antibodies in this PsA population failed to reach statistical significance. However, when present, they were a marker of disease severity and had RA-linked MHC class II associations. Further studies are needed in a larger population of patients with PsA and appropriate controls to confirm any true association that may be present.
authors.affiliation: Royal National Hospital for Rheumatic Diseases, Upper Borough Walls, Bath BA1 1RL, UK.
authors.forename: E
authors.initials: E
authors.lastname: Korendowych
authors.forename: P
authors.initials: P
authors.lastname: Owen
authors.forename: J
authors.initials: J
authors.lastname: Ravindran
authors.forename: C
authors.initials: C
authors.lastname: Carmichael
authors.forename: N
authors.initials: N
authors.lastname: McHugh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015535:Arthritis, Psoriatic / Q000235:genetics / Q000276:immunology*; D001172:Arthritis, Rheumatoid / Q000276:immunology; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D005260:Female; D006684:HLA-DR Antigens / Q000097:blood; D059811:HLA-DRB1 Chains; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D011446:Prospective Studies; D012217:Rheumatoid Factor / Q000097:blood; D012720:Severity of Illness Index
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor