title: A retrospective study of the fluctuation in serum levels of anti-cyclic citrullinated peptide antibody in patients with rheumatoid arthritis.
abstract: OBJECTIVE
  To investigate the fluctuation in serum levels of anti-cyclic citrullinated peptide antibody (anti-CCP) retrospectively in patients with rheumatoid arthritis (RA).
  
  
  METHODS
  Serum levels of anti-CCP were measured retrospectively in 131 patients with RA and 90 patients with non-RA rheumatic diseases using a commercially available kit. All sera were collected from patients during the 22-year period, 1982-2004. To analyze the fluctuation in anti-CCP levels, 17 RA patients were selected on the basis of showing a significantly higher anti-CCP level in a serum sample taken at the first visit (> 80 U/ml), and availability of preserved serum samples that had been taken from each patient at 10 time points.
  
  
  RESULTS
  The test gave a sensitivity of 88% (115/131) and a specificity of 81% (73/90). The longitudinal study of 17 RA patients showed that anti-CCP levels were elevated at the first visit in 12 (71%) patients and then decreased gradually, whereas those in the other five (29%) patients fluctuated substantially. In both cases, anti-CCP levels tended to fluctuate in parallel with the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level, reflecting the spontaneous aggravation of arthritis and the efficacy of anti-rheumatic drugs. The courses of three representative RA patients are illustrated in detail along with their therapeutic regimens, and these further confirm the correlation of anti-CCP levels with laboratory parameters (ESR and CRP) as well as the activity of arthritis.
  
  
  CONCLUSIONS
  Measurement of serum anti-CCP levels was found to be useful for not only the diagnosis but also the management of RA.
authors.affiliation: Department of Clinical Immunology, Clinical Research Institute, International Medical Center of Japan, Shinjuku-ku, Tokyo, Japan. aotsuka@ri.imcj.go.jp
authors.forename: S
authors.initials: S
authors.lastname: Aotsuka
authors.forename: M
authors.initials: M
authors.lastname: Okawa-Takatsuji
authors.forename: K
authors.initials: K
authors.lastname: Nagatani
authors.forename: C
authors.initials: C
authors.lastname: Nagashio
authors.forename: T
authors.initials: T
authors.lastname: Kano
authors.forename: K
authors.initials: K
authors.lastname: Nakajima
authors.forename: K
authors.initials: K
authors.lastname: Ito
authors.forename: A
authors.initials: A
authors.lastname: Mimori
mesh_terms: D000974:Antibodies, Antinuclear / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000097:blood*; D015415:Biomarkers; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D011933:Reagent Kits, Diagnostic; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D000974:Antibodies, Antinuclear; D015415:Biomarkers; D010456:Peptides, Cyclic; D011933:Reagent Kits, Diagnostic; C487763:cyclic citrullinated peptide