At the time of diagnosis, some laboratory examinations help to better define the type of JIA (Juvenile Idiopathic Arthritis) a patient is suffering from. They can also help to identify patients at risk of developing some complications, such as chronic iridocyclitis.
Rheumatoid factor (RF) is an autoantibody that is positive and in high concentration only in the polyarticular form of JIA, which is the childhood equivalent of RF positive adult rheumatoid arthritis.
Antinuclear antibodies (ANA) are frequently positive in patients with oligoarticular early-onset JIA. This identifies JIA patients at high risk of developing chronic iridocyclitis and who have to have an ocular examination with a slit lamp every three months.
HLA-B27 is a cellular marker that is positive in up to 80% of patients with enthesitis associated arthritis. Its frequency in the general, healthy population is much lower (5-8%).
Other exams, such as erythrocyte sedimentation rate (ESR), or C-reactive protein (CRP), measure the extent of general inflammation and are useful in disease management, along with clinical examinations.
Periodic X-ray examinations are useful to assess potential disease progression and, therefore, to ensure the therapeutic regimen remains appropriate.
Depending on the drug regimen, patients may need periodic laboratory examinations to assess potential drug toxicity.