Anti-cyclic citrullinated peptide antibodies in patients with juvenile idiopathic arthritis.

We analysed the presence of anti-cyclic citrullinated peptide (anti-CCP) and anti-keratin (AKA) antibodies of the IgG class in sera of patients with defined juvenile idiopathic arthritis (JIA) of various subgroups with more than one year duration of the disease. Enzyme-linked immunosorbent assay (Immunoscan RA, Eurodiagnostica, The Netherlands) and an indirect immunofluorescence (IIF) test on rat oesophagus substrate (ImmuGloTM, Immco Diagnostics, Buffalo, USA) were used for the detection and quantification of anti-CCP and AKA antibodies in 140 patients with JIA (64 male and 76 female) aged 2-47 years (median 16.5 years). Overall, anti-CCP were found in 7/140 (5.0%) patients including 3/52 RF negative polyarthritis, 2/18 RF positive polyarthritis, 1/15 enthesitis related arthritis and 1/5 unclassifiable arthritis. AKA were detected in 40/140 patients (28.6%, p = 0.04) including 2/11 systemic arthritis, 2/32 oligoarthritis, 18/52 patients with RF negative polyarthritis (34.6%, p = 0.01), 14/18 RF positive polyarthritis (77.8%, p = 0.000002), 2/15 enthesitis related arthritis and 2/3 psoriatic arthritis. While simultaneous negativity for AKA and anti-CCP occurred in most (97/140; 69.3%) studied cases, simultaneous antibody positivity was found only in few (4/140; 2.9%) studied samples. We conclude that while AKA measured using IIF on rat esophagus can be detected approximately in one third of patients with definite JIA with more than 1 year duration of the disease, only rare occurrence of anti-CCP was observed. We conclude that AKA seem to be partly useful to confirm JIA diagnosis, however, useless to follow-up severity or activity in JIA patients. Anti-CCP do not have any additional value in MA cohort in comparison to RA where their diagnostic and prognostic importance was reported.