Juvenile chronic arthritis. A study on epidemiology and outcome in Costa Rican children

Sammanfattning: Problems associated with interpreting and comparing epidemiological studies dealing with chronic arthropathies in children include the diversity of classification criteria and selection bias. This study is a step towards elucidating the impact of genetic and environmental factors on disease frequencies and manifestations of Juvenile Chronic Arthritis (JCA) in Costa Rica. The present research also aims to investigate the influence of JCA on health-related quality of life in Costa Rican children. Costa Rica is a transitional society, still undeveloped economically, but with a high educational and health care standard.Firstly, a prospective pilot referral study on JCA was conducted for the whole country. The incidence of JCA found, 5.4 per 100,000, was low compared with other population-based studies. Difficulties such as poor communications with some areas and inadequate knowledge of chronic autoimmune diseases among medical personnel were speculated as being possible factors explaining the low incidence.The second phase included a prospective population-based study conducted in the urban area of San José, the capital of Costa Rica, from 1993 to 1995 and a parallel two-year educational program on childhood arthritis for the health personnel working in the catchment area. A low incidence (6.8/100 000, 95% CI 4.1-9.6) and prevalence (31.4/100 000, 95% CI 25.5-37.2, excluding those in remission) of JCA were found. Other findings were differences in subtype distribution with, as in the first report, a lack of oligoarticular preschool girls and low rates of ANA positivity and uveitis compared with studies from Caucasian populations.In the third phase, the Childhood Health Assessment of Questionnaire (CHAQ) was validated for use in Costa Rican children. It proved to be a feasible, reliable and valid instrument for measuring the functional impact of JCA on Costa Rican children.Forty-seven JCA children were collected in the prospective incidence study and 49 children from the cross-sectional group participated in the fourth phase, the follow-up study. In both groups, the proportion of subtype switching during the course of the disease was very low and in all cases the switch occurred within the first two years after disease onset. The risk of developing uveitis remained low during the course of the disease. The involvement of proximal interphalangeal joints was related with an increased risk of continuing disease activity. The children with oligoarticular disease course had a higher chance of no continuing disease activity at follow-up when compared with the other subtypes (RR 2.8, 95% CI 1.2-6.9). Forty-eight percent of the patients showed persistent disease activity at the moment of transition to adult care. During the fifth phase, the same children were followed in order to study the impact of JCA on health-related quality of life aspects. At the end of follow-up, 85% percent of the patients in the incidence group indicated some difficulty in daily activities. The strongest determinant for disability was continuing disease activity. Girls reported more pain and more psychosocial impact due to JCA than boys. Oligoarticular disease at follow-up was linked to milder outcome and less psychosocial impact. The majority of the families reported a high degree of influence of the disease on the family economy and working life.Conclusions: In comparison with other population-based studies, we found a lower incidence and prevalence of JCA and an absence of the typical ANA positive early onset oligoarticular form. Uveitis at onset and during the disease course was also rare. The strongest determinant for disability was continuing disease activity. Even in this unselected population, the majority of patients reported at follow-up some difficulty in the CHAQ. Special services for children affected with JCA are lacking in Costa Rican society.

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