Findings from a physical examination, including the pattern and nature of joint symptoms, are important keys to the diagnosis of juvenile rheumatoid arthritis (JRA). In most cases, routine lab results do not point to an obvious diagnosis of this disease. JRA is often diagnosed only after other possible causes of symptoms have been ruled out and the pain and stiffness have lasted for at least 6 weeks. The following tests are mainly done to see whether another medical condition is causing joint pain or whole-body (systemic) symptoms.

Routine examinations and tests include the following:

• Medical history and physical examination
• Complete blood count (CBC)
• Erythrocyte sedimentation rate (ESR, or sed rate)
• Urinalysis
• Rapid strep test or throat culture (to test for strep throat)

The following tests are done if needed:

• Rheumatoid factor (RF), to clarify whether a child with polyarticular JRA is RF-positive or RF-negative
• Antinuclear antibody (ANA), to clarify a child's type of JRA and risk for eye disease (a positive ANA result is a marker for high eye disease risk, usually found in girls who develop pauciarticular JRA at a young age)
• X-ray
• Magnetic resonance imaging (MRI), which may reveal early joint damage
• Human lymphocyte antigen or HLA-B27 genetic test, which may help distinguish JRA from other types of arthritis that affect children, such as ankylosing spondylitis

Early Detection

There are no standard screening tests that are used to identify children who may develop juvenile rheumatoid arthritis (JRA).

Early eye disease detection

Slit lamp eye examinations are necessary for all children with juvenile rheumatoid arthritis to test for possible eye problems, such as uveitis. This test may be repeated often during the course of the condition because the inflammatory eye disease associated with JRA generally has no symptoms and can lead to a permanent decrease in vision or blindness.

Inflammatory eye disease risk is not related to how severe a child's other JRA symptoms are. In fact, children at greatest risk are girls who develop mild pauciarticular disease (oligoarthritis) during their early childhood years and have developed high levels of antinuclear antibodies (ANAs).