Comparison of criteria for the classification of childhood arthritis

Objective. To evaluate the applicability of the ILAR criteria for classific ation of childhood arthritis in an outpatient pediatric rheumatology clinic population, and to determine the proportion of children who met standard c lassification criteria, but failed to meet ILAR criteria for specific arthr itides, and therefore became unclassifiable. Methods. We reviewed the charts of 70 consecutive patients who had arthriti s for at least 6 months, and attended the clinic between September and Nove mber 1997. Sixty-nine patients were categorized according to one of the tra ditional classifications [ACR for juvenile rheumatoid arthritis (JRA), Euro pean Spondylarthropathy Study Group (ESSG) for spondyloarthropathy, Vancouv er Criteria for juvenile psoriatic arthritis (JPsA)], and the ILAR classifi cation system. Results. Sixty-one patients (88.4%) were classifiable by the ILAR system; 8 others failed to fulfill ILAR criteria for any specific category, and were assigned to the "other arthritis" category. Of the 29 patients with oligoa rticular onset JRA, 6 were unclassified, 5 because of exclusions, and one b ecause he fulfilled criteria for 2 categories. Presence of a family history of psoriasis accounted for most of the exclusions in the oligoarthritis an d enthesitis related arthritis categories. All patients with polyarticular onset or systemic onset JRA were classified in the corresponding category i n the ILAR system. One 9-year-old patient with spondyloarthropathy was recl assified as "other arthritis" because of exclusions. All 6 children with de finite JPsA met ILAR criteria for PsA. Of 4 patients with probable JPsA, on ly 2 met ILAR criteria for PsA, a third was classified as rheumatoid factor negative polyarthritis, and the fourth was classified as "other arthritis" because of exclusions. Conclusion. The ILAR classification criteria applied to a group of children with chronic arthritis classified by traditional criteria results in reass ignment of 11.6% of the patients, predominantly in the oligoarticular group . It will be important to determine the role of the presence of a family hi story of psoriasis in classifying these patients.