title: The relationship between peripheral arthritis and anti-cyclic citrullinated peptide antibodies in ankylosing spondylitis.
abstract: OBJECTIVE
  Although ankylosing spondylitis (AS) primarily affects the axial skeleton, peripheral arthritis occurs in up to 35% of cases. Anti-cyclic citrullinated peptide (anti-CCP) antibodies are highly specific for rheumatoid arthritis, whereas their role in AS remains unclear. In this study we aimed to assess the prevalence of anti-CCP antibodies in AS patients with peripheral arthritis and their clinical association with peripheral arthritis.
  
  
  METHODS
  We retrospectively selected for this study 625 AS patients who fulfilled the modified New York criteria. The patients were divided into those with and those without peripheral arthritis on smoking history, the basis of symptoms, physical examination and medical records. The presence of anti-CCP antibodies was investigated in all the patients.
  
  
  RESULTS
  Anti-CCP antibodies were found in 4% (25/625) of the patients, and peripheral arthritis was diagnosed in 37.4% (234/625) of the patients. In multiple logistic regression, peripheral arthritis was significantly associated with female gender (P = 0.001) and the presence of anti-CCP antibodies (P = 0.001), especially with the presence of titers of anti-CCP antibodies over three times the normal upper limit of the laboratory and assay.
  
  
  CONCLUSIONS
  Anti-CCP antibodies are occasionally present in AS, and their presence may be helpful as a serum marker for predicting peripheral arthritis.
authors.affiliation: Department of Internal Medicine, Hanyang University Hospital, Seoul, Republic of Korea.
authors.forename: Jin-Ok
authors.initials: JO
authors.lastname: Kim
authors.forename: Ji-Seon
authors.initials: JS
authors.lastname: Lee
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Choi
authors.forename: Kyu Hoon
authors.initials: KH
authors.lastname: Lee
authors.forename: Yong-Bum
authors.initials: YB
authors.lastname: Kim
authors.forename: Dae-Hyun
authors.initials: DH
authors.lastname: Yoo
authors.forename: Tae-Hwan
authors.initials: TH
authors.lastname: Kim
mesh_terms: D000328:Adult; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D001168:Arthritis / Q000097:blood / Q000453:epidemiology* / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D015897:Comorbidity; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D010456:Peptides, Cyclic / Q000276:immunology*; D011237:Predictive Value of Tests; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D013167:Spondylitis, Ankylosing / Q000097:blood / Q000453:epidemiology* / Q000276:immunology*
chemical_list: D000888:Antibodies, Anti-Idiotypic; D015415:Biomarkers; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide
keywords: Ankylosing spondylitis; Anti-CCP antibody; Peripheral arthritis