title: Effect of age on prevalence of anticitrullinated protein/peptide antibodies in polyarticular juvenile idiopathic arthritis.
abstract: OBJECTIVE
  Anticitrullinated protein/peptide antibodies (ACPA) have an excellent diagnostic performance for rheumatoid arthritis (RA). Despite similarities between RA and polyarticular juvenile idiopathic arthritis (JIA), the prevalence of ACPA in polyarticular JIA is low. We wanted to evaluate the influence of age, disease duration and total immunoglobulin G (IgG) concentration on ACPA positivity in this cohort.
  
  
  METHODS
  Patients with JIA were classified according to age and International League of Associations for Rheumatology classification. Sixty-one JIA patients aged less than 16 yr were included and classified as polyarticular JIA (poly JIA <16; n=23) or non-polyarticular JIA (n=38). In addition, a group of 21 polyarticular JIA patients, aged more than 16 yr (poly JIA >16) and a group of 51 RA patients were included. Antibodies to the synthetic citrullinated peptides pepA and pepB were detected by line immunoassay and antibodies to cyclic citrullinated peptides (CCP2) by enzyme-linked immunosorbent assay. Serum IgG was measured by fixed-time immunonephelometry.
  
  
  RESULTS
  No ACPA reactivity was observed in the non-polyarticular group. In poly JIA <16, only 1/23 had anti-CCP2 antibody, whereas in poly JIA >16 patients a significantly higher fraction was detected (6/21). All but one of the anti-CCP2 reactive patients were rheumatoid factor (RF) positive. Assessing anti-CCP2 antibody concentration as a continuous variable, significantly higher titres were found in poly JIA >16 compared with poly JIA <16. No correlation between anti-CCP2 concentration and total IgG was detected. Four patients demonstrated immunoreactivity against pepA and pepB; all of them were anti-CCP2 reactive, poly JIA >16 patients.
  
  
  CONCLUSIONS
  ACPA are present in low prevalence in polyarticular JIA and are particularly found in the RF-positive subset. With age, a significant increase in anti-CCP2 positivity is observed in polyarticular JIA patients.
authors.affiliation: Department of Rheumatology, Ghent University Hospital, De Pintelaan 185, 9000 Gent, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Dewint
authors.forename: I E A
authors.initials: IE
authors.lastname: Hoffman
authors.forename: S
authors.initials: S
authors.lastname: Rogge
authors.forename: R
authors.initials: R
authors.lastname: Joos
authors.forename: A
authors.initials: A
authors.lastname: Union
authors.forename: J
authors.initials: J
authors.lastname: Dehoorne
authors.forename: J
authors.initials: J
authors.lastname: Delanghe
authors.forename: E M
authors.initials: EM
authors.lastname: Veys
authors.forename: F
authors.initials: F
authors.lastname: De Keyser
authors.forename: D
authors.initials: D
authors.lastname: Elewaut
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001171:Arthritis, Juvenile / Q000276:immunology*; D001172:Arthritis, Rheumatoid / Q000276:immunology; D001323:Autoantibodies / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D004745:Enkephalins / Q000276:immunology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008297:Male; D008875:Middle Aged; D015688:Oncogene Protein pp60(v-src) / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology; D010456:Peptides, Cyclic / Q000276:immunology*; D011498:Protein Precursors / Q000276:immunology
chemical_list: D001323:Autoantibodies; D004745:Enkephalins; D007074:Immunoglobulin G; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D011498:Protein Precursors; C487763:cyclic citrullinated peptide; C098708:peptide A; C056943:peptide B; D015688:Oncogene Protein pp60(v-src)