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2 Classification of juvenile idiopathic arthritis
  2. R HÄFNER,
  1. Paediatric Rheumatology Hospital, Garmisch-Partenkirchen
    1. Chair of Rheumatology of the University of Milan, Centre for Rheumatic Children, Gaetano Pini Institute, Milan, Italy
      1. Department of Paediatrics, University of Göteborg and Falun's Hospital, Sweden
        1. J DEHOORNE,
        2. B VANNEUVILLE,
        3. R JOOS,
        4. J VANDE WALLE,
        5. EMVEYS
        1. Centre for Paediatric Rheumatology, University Hospital, Gent, Belgium

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          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 them with antinuclear antibodies, 7 with chronic uveitis), resembling oligoarthritis. We therefore suggest an extra category “extended oligoarthritis”.

          Conclusion—About 85% of our patients with JIA could readily be classified into one of the defined categories. With minor changes in the definition this percentage would increase to over 90%. Introduction of a further category for extended oligoarthritis with asymmetric arthritis of 5 to 8 (9) joints at onset should be considered.

          2.2 Classification of juvenile idiopathic arthritis: suggestions to improve the efficacy of the Durban criteria

          The Durban Classification Criteria for juvenile idiopathic arthritis (JIA) were tested on a cohort of 683 patients (220 male, 463 female) with juvenile onset primary chronic arthritides recorded in the database of our centre. 214 cases fell into the category of “other arthritis”. To reduce the number of cases in this category, two ways were suggested to (a) reduce the exclusions and (b) to consider a hierarchy of the categories.

          According to the data of our patients, the exclusions which most commonly hinder an obvious classification are (a) family history of psoriasis in at least one first or second degree relative (for oligoarthritis); (b) psoriasis confirmed by a dermatologist in at least one first or second degree relative (for enthesitis related arthritis); (c) oligoarticular onset for rheumatoid factor (RF) positive polyarthritis.

          The hierarchy principle states that if a patient fits into more than one category, he or she should be attributed to the category with the highest rank. In attributing ranks, two general principles might be taken into account: (a) the more severe form should be preferred to the less severe one; (b) the more differentiated form (that is better biologically and/or clinically characterised) should be preferred to the less differentiated one. According to our data the most useful ranking might be: (1) systemic arthritis; (2) RF positive polyarthritis; (3) psoriatic arthritis; (4) enthesitis related arthritis; (5) oligoarthritis; (6) RF negative polyarthritis.

          If the hierarchy principle were accepted, slightly modified Durban criteria would classify almost all patients with JIA and each category would maintain a fruitful and valuable homogeneity.

          2.3 Evaluation of Durban Classification Criteria for juvenile idiopathic arthritis (JIA) in Spanish children

          Objective—To test the proposed Durban Classification Criteria for juvenile idiopathic arthritis (JIA) in a cohort of Spanish children.

          Methods—125 patients seen between January 1999 and March 2000 were classified according to the following criteria: EULAR for pauciarticular (paJCA), polyarticular (poJCA), poJCA RF positive (po-RF+), and systemic (sJCA) arthritis; Vancouver for psoriatic arthritis (PsA); and ESSG for juvenile spondyloarthropathy (JSp). Patients were reclassified according to Durban criteria, and their clinical/serological characteristics were reviewed.

          Results—Table 3-1 shows the results obtained.

          View this table:
          Table 3-1

           Patients classified according to the Durban criteria

          Discussion—Application of Durban criteria results in a significant number of unclassified patients. According to these criteria, 14/125 of our patients (11%) fell into the “other arthritis” category, 13/14 because of a positive family history of psoriasis.

          Interestingly, a 2nd degree family history of psoriasis does not fit the “psoriatic arthritis” criteria, but allows classification of patients into the “poly RF negative” category.

          No differences were found in any variable studied between patients classified as “oligo” (n=47) and those with oligoarticular onset included in “other arthritis” group (n= 11), except for a family history of psoriasis.

          2.4 JCA in the Nordic countries; a population based multicentre study of construct validity of ILAR, in comparison with EULAR classification criteria

          Background—Childhood chronic arthritis is a heterogeneous group of disorders. New classification criteria (ILAR), for “juvenile idiopathic arthritis” (JIA), have been proposed. They are more descriptive than those formerly used (ACR-JRA, EULAR-JCA) but need validation under “appropriate epidemiological and statistical direction against classifications already in use”.

          Objective—To compare construct validity of ILAR and EULAR classification criteria in a cohort of prospectively collected incidence cases of “juvenile chronic arthritis” within 15 defined areas of Sweden, Finland, Norway, Denmark, and Iceland. The cases were collected during one and a half years, beginning 1 July 1997.

          Method—Clinical variables (including those constituting the EULAR and ILAR criteria) and laboratory findings were registered longitudinally for each patient by paediatricians experienced in paediatric rheumatology. A database was constructed specifically for this purpose. In this study clinical findings and laboratory data from the first 6 months (for certain variables also for the first 12 months) were considered.

          Results—322 patients qualified for classification according to the ILAR criteria. Of those 322 patients, 291 had a disease duration of >3 months and were classified according to the EULAR criteria. Thus, 31/322 (10%) children were diagnosed only according to the ILAR criteria. 15% of the patients did not fulfil ILAR criteria for any of the categories and 6% fulfilled criteria for more than one category. As an example of the effect of different classification systems in our study, 160/322 were classified as oligoarticular by ILAR criteria and 184/291 by EULAR criteria.

          Conclusion—The qualifications for the ILAR criteria are different from those of the EULAR criteria, which makes simple comparison neither possible nor scientifically relevant. One possibility is to study the construct validity of the respective criteria to give us a better idea of the classification and its consequences.

          2.5 Juvenile spondyloarthropathies: checking criteria for diagnosis and classification at the start and after 6 months of disease

          Classification of juvenile spondyloarthropathies remains a “critical” point in paediatric rheumatology.

          Objective—To validate classification methods in a university hospital treated population by a retrospective cross sectional study.

          Methods— Four sets of criteria especially designed for juvenile patients (Garmisch-Partenkirchen-JSA, SEA syndrome, enthesitis related arthritis, atypical spondarthritis) and two sets of criteria for patients without age specification (ESSG, Amor) were checked in a group of 20 patients at the start of disease and after six months.

          Statistics—The sensitivity and specificity were calculated as well as the reproducibility after six months.

          Results—The preliminary results show equal sensitivities for all sets except for the SEA syndrome criteria (which was the lowest). Although in some patients a switch to other types of juvenile chronic arthritis occurred, the initial fulfilment of the criteria was highly predictive for the fulfilment after six months.

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