To evaluate the proposed International League of Associations for Rheumatology (ILAR) classification criteria for juvenile idiopathic arthritis in a cohort of Spanish children.
One hundred twenty-five patients with chronic arthritis were categorized according to one of the traditional classifications and the proposed ILAR classification system after at least 6 months of disease. The traditional classifications included the European League Against Rheumatism (EULAR) criteria for pauciarticular, polyarticular rheumatoid factor (RF) negative, and systemic juvenile chronic arthritis (JCA), as well as for RF+ polyarthritis; the Vancouver criteria for juvenile psoriatic arthritis (JPsA); and the European Spondylarthropathy Study Group (ESSG) preliminary criteria for juvenile spondyloarthropathy (JSpA).
The ILAR criteria classified 106/125 patients (84.8%). All patients with systemic and polyarticular JCA, RF+ polyarthritis, and definite juvenile psoriatic arthritis were reclassified in the corresponding ILAR category. In contrast, only 80% of pauciarticular JCA and 47% of JSpA patients could be allocated to the ILAR oligoarthritis (47/59 patients, 35 persistent and 12 extended) and enthesitis related arthritis (ErA. 8/17 patients) categories. Two children with probable PsA were reclassified in the RF- polyarthritis category. Nineteen patients (15.2%) were allocated to the ILAR "other arthritis" group, 13/19 because they did not fulfill criteria for any of the other categories (12 due to family history of psoriasis and one because of family history of HLA-B27 associated disease). The remaining 6 patients met criteria for 2 categories, RF- polyarthritis and either ErA (n = 5) or PsA (n = 1). No differences other than family history of psoriasis were found in any of the variables studied between pauciarticular JCA patients classified in the oligoarthritis (n = 47) and those in the "other arthritis" (n = 11) ILAR categories.
The proposed ILAR criteria allocated 84.8% of the patients classified by traditional criteria. Family history of psoriasis (n = 12) and polyarticular onset of disease in patients with ErA (n = 5) were responsible for most of the exclusions from other ILAR categories.