2.1 Evaluation of classification criteria for juvenile idiopathic arthritis (JIA)

The new classification of JIA means a valuable contribution for international exchange. The definition of distinct categories enables studies of homogeneous groups of patients in the future. Our task at present is to validate the classification criteria.

We therefore categorised a total of 172 consecutive patients with JIA who were treated in our hospital in October 1999.

Results—145 patients fulfilled criteria for one of the defined categories: 30 systemic JIA, 47 oligoarthritis (19 of them with extended oligoarticular course), 44 rheumatoid factor (RF) negative and 5 RF positive polyarthritis, 11 enthesitis related arthritis, and 8 psoriasis arthritis. 27 were classified as “other arthritides”. 11 did not fulfil criteria for any one category, 16 fulfilled criteria for two categories. Double classification occurred mainly in patients with psoriasis or enthesitis.

Discussion—(1) 6 of the 11 patients who did not fit into one category could be classified as oligoarthritis, but a family history of psoriasis excluded them and criteria for psoriasis arthritis were not fulfilled.

(2) 5 of the 16 patients who met criteria for two categories could be classified in one (psoriasis arthritis) if psoriasis is an exclusion for oligoarthritis, RF negative polyarthritis, and enthesitis related arthritis. The other 11 patients had enthesitis and arthritis but also fulfilled criteria for either oligoarthritis or RF negative polyarthritis.

(3) 25 children categorised as RF negative polyarthritis had asymmetric arthritis of 5 to 8 joints at onset (18 of …