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Prevalence and incidence of JIA

Clinical bottom line

The prevalence of JIA is about 6 in 10,000 children. The annual incidence of JIA is about 1 per 10,000 children.


Background

Epidemiology of chronic disease is important, especially for healthcare planning. Changes in diagnosis and treatments can mean that previously little-considered conditions can increase in numbers of patients and in costs of treatment by orders of magnitude over relatively short timescales. For sensible planning and horizon scanning, we need to have a sensible idea of how many patients with chronic diseases exist, or are likely to occur.

Juvenile arthritis could be one such consition. Newer biological treatments like anti-TNF agents have been shown to be effective in rheumatoid arthritis, both late and early in its course. Expanding research into juvenile arthritis could lead to large demands for expensive treatments over long periods.

Reference

PJ Manners, C Bower. Worldwide prevalence of juvenile arthritis - why does it vary so much? Journal of Rheumatology 2002 29: 1520-1530.


Review

Two electronic databases were searched for studies that might comment of prevalence or incidence of juvenile arthritis, using a number of different terms for juvenile arthritis, such as juvenile rheumatoid, chronic, or idiopathic arthritis. Only English-language articles were sought.

Results

Thirty-four articles were found, from 1966 to 1998. Definitions of disease varied, as did the method of case ascertainment, including hospital records, questionnaires, statistical databases, and insurance records. The size of studies (in terms of prevalent case, also varied, from as few as two, to as many as 330.

The reported prevalence varied from 0.07 to 4 per 1000 children. Figure 1 shows the results according to number of prevalent cases where that information was available. Most of the variability came from small studies, and the overall mean prevalence weighted by the number of prevalent cases was 0.6 per 1000 children, or 6 per 10,000 children.

Figure 1: Prevalence of juvenile arthritis by number of prevalent cases

The reported annual incidence varied from 0.008 to 0.23 per 1000 children. Figure 2 shows the results according to number of prevalent cases where that information was available. Most of the variability came from small studies, and the overall mean incidence weighted by the number of prevalent cases was 0.09 per 1000 children, or 1 per 10,000 children.

Figure 2: Incidence of juvenile arthritis by number of prevalent cases

Comment

What was interesting is that each of the studies was commented on in some detail, so this review would be a terrific place to start understanding some of the variability in prevalence and incidence estimates. These were:

  1. Different diagnostic criteria were applied over the 30 years of study reporting.
  2. There were different means of case ascertainment.
  3. Size differed significantly between studies.