Investigations for patients with confirmed JIA

The following blood investigations should only be performed in children or adolescents with inflammatory arthritis. If there is uncertainty about the child’s presentation, see instead Assessment of musculoskeletal symptoms in children and adolescents. Do not use the following tests to screen for JIA in children or adolescents whose only musculoskeletal symptoms are joint aches and pain—they can be positive in healthy children and are neither sensitive nor specific enough to confirm or exclude inflammatory arthritis.

In patients with JIA, the following tests are used by specialists to help classify disease and assess the risk of complications:

• antinuclear antibodies (ANA)—children or adolescents with JIA often have a positive ANA result, but up to 15% of healthy children do too. In patients with JIA, a positive ANA is a risk factor for developing asymptomatic anterior uveitis, particularly in those with oligoarticular disease
• rheumatoid factor (RF) and antibodies to cyclic citrullinated peptides (CCP)—a minority of children or adolescents with polyarthritis are RF positive or have CCP antibodies. Similar to its prognostic role in adults with rheumatoid arthritis, RF positivity in children and adolescents suggests poor prognosis
• human leucocyte antigen B27 (HLA-B27)—HLA-B27 is a diagnostic feature of enthesitis-related arthritis, but is not useful in isolation because it is also present in about 10% of the normal Australian population. The significance of a positive test result is determined by the patient’s clinical presentation; in a child or adolescent with symptoms suggestive of an enthesopathy, a positive result is likely to be significant.