OBJECTIVES: 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.