PREVALENCE OF JUVENILE CHRONIC ARTHRITIS IN A POPULATION OF 12-YEAR-OLD CHILDREN IN URBAN AUSTRALIA

Objective. To conduct a cross-sectional, community-based, point preval ence study of inflammatory joint disease and other rheumatic disorders in 12-year-old children in a metropolitan community. Methods. After c ompletion of a pilot study of 816 10-year-old children, a cross-sectio nal prevalence study was performed 2 years later on a randomized sampl e of 2241 12-year-old children (including the cohort from the pilot st udy) from a community of approximately 221 700 children aged 12 years or younger, with 17 300 children aged approximately 12 years. A rheuma tologic examination was performed on each child by a single observer a fter perusal of completed questionnaires from parents and children. Re sults. Three of 816 children in the pilot study were shown to have juv enile chronic arthritis (JCA), fulfilling the criteria of the European League Against Rheumatism for the diagnosis of JCA. Only 1 of 3 had a previous diagnosis of JCA. The prevalence was 3.7 per 1000. Of 2241 c hildren examined 2 years later, 89% returned two questionnaires (one c ompleted by the parent and one by the child). At examination, 38 swoll en joints were identified in 32 children. Nine children were identifie d with JCA, of whom 7 had not had previous diagnoses. No questions fro m the questionnaires identified the 7 children with previously undiagn osed JCA. The point prevalence of JCA in this community was 4.0 per 10 00. Although the children with newly diagnosed cases tended to have mi ld disease, it was associated with significant morbidity and the poten tial for serious morbidity. Conclusions. This is the first reported pr evalence study of JCA in which case ascertainment was based on clinica l examination by a rheumatologist of children within a community. The prevalence of 4.0 per 1000 was significantly higher than the accepted prevalence of 0.6 to 1.1 per 1000. A study based on known cases would have significantly underestimated the true prevalence of JCA in this c ommunity, with 7 of 9 cases being previously undiagnosed. Questionnair es were not effective in identifying children with undiagnosed JCA, cl inical examination supported by a history from the parent and child pr oviding the only reliable means of diagnosis. It is possible throughou t the world that the numbers of undiagnosed cases of JCA significantly exceed the numbers of known cases, with the true prevalence being sig nificantly higher than the levels currently accepted.