title: Profiling anti-cyclic citrullinated peptide antibodies in patients with juvenile idiopathic arthritis.
abstract: BACKGROUND
  Anti-citrullinated protein/peptide antibodies (ACPA), have high specificity for rheumatoid arthritis (RA). Some children with juvenile idiopathic arthritis (JIA), phenotypically resemble RA and test positive for rheumatoid factor (RF) a characteristic biomarker of RA. We investigated the prevalence of ACPA and its relationship to other serologic markers associated with RA in a well-characterized JIA cohort.
  
  
  METHODS
  Cases were 334 children with JIA, 30 of whom had RF + polyarticular JIA. Sera from all cases and 50 healthy pediatric controls were investigated by ELISA at a single time point for anti-cyclic citrullinated peptide (anti-CCP) IgG, RF IgM, IgA and IgG, anti-RA33 IgG, and antinuclear antibodies (ANA). Comparisons between cases and controls were made using Chi-square or Fisher exact tests and T-tests.
  
  
  RESULTS
  The prevalence of RF was 8% among controls, and 12% among cases (ns). The prevalence of ACPA was 2% in controls and 14.3% in cases (OR 8.2, p <0.01). Children who were ACPA-positive and RF-negative (n = 23) had a significantly earlier onset-age (4.6 years vs. 12.1 years, p <0.00001) and had fewer HLA-DRB1 shared epitope alleles than those positive for both RF and ACPA (n = 25). Prevalence of anti-RA33 was not different between cases and controls.
  
  
  CONCLUSIONS
  ACPAs are detectable in 14% of children with JIA. Children with positive ACPA but negative RF are frequent, and may define a distinct subset of children with JIA. ACPA testing should be included in the classification of JIA.
authors.affiliation: Department of Pediatrics and Human Genetics, Emory University School of Medicine, 2015 Uppergate Drive NE, Atlanta, GA, 30322, USA. sprahal@emory.edu.
authors.forename: Anne E
authors.initials: AE
authors.lastname: Tebo
authors.forename: Troy
authors.initials: T
authors.lastname: Jaskowski
authors.forename: K Wayne
authors.initials: KW
authors.lastname: Davis
authors.forename: April
authors.initials: A
authors.lastname: Whiting
authors.forename: Bronte
authors.initials: B
authors.lastname: Clifford
authors.forename: Andrew
authors.initials: A
authors.lastname: Zeft
authors.forename: Bernadette
authors.initials: B
authors.lastname: McNally
authors.forename: Harry R
authors.initials: HR
authors.lastname: Hill
authors.forename: John
authors.initials: J
authors.lastname: Bohnsack
authors.forename: Sampath
authors.initials: S
authors.lastname: Prahalad