The goals of testing are to help diagnose juvenile rheumatoid arthritis (JRA), to distinguish it from other forms of arthritis and conditions with similar symptoms, and to evaluate its severity. Testing can be used to monitor the condition, its potential complications, response to treatment, and to monitor for potential side effects associated with some treatments.
Diagnosis of JRA is based on medical exam, including review of clinical signs and symptoms, such as persistent arthritis in one or more joints for at least six weeks that cannot be attributed to another cause. Those affected may also have an enlarged liver or spleen, swollen lymph nodes, anemia, heart problems, and eye inflammation.
Laboratory tests that can aid in the diagnosis of JRA include the following, although many children with JRA will not have any abnormal findings on these:
- Antinuclear antibody (ANA) – to detect the presence of autoantibodies; most common test to be positive in children with JRA; about 80% of those with eye involvement will test positive for ANA.
- Rheumatoid factor (RF) – may be positive or negative depending on the type of juvenile arthritis a child has; more commonly found in adults with rheumatoid arthritis
- Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) – to detect inflammation in the body
- Complete blood count (CBC) – to evaluate a child's red and white blood cells and hemoglobin to help evaluate and monitor the condition and complications, such as anemia and/or a decreased white blood cell count
- Comprehensive metabolic panel (CMP) – to help evaluate and monitor a child's kidney and liver function
Other lab tests that may be performed to rule out other conditions with similar symptoms include:
- HLA-B27 – a genetic test that can help to distinguish the type of arthritis affecting a child, such as a type that affects the spine (ankylosing spondylitis)
- Synovial fluid analysis – sometimes ordered to detect crystals that may be present in the joint and to look for signs of joint infection
- Blood culture – to rule out infection
- Other laboratory tests, such as a test for Lyme disease, as appropriate
- X-rays of the joints and chest – to identify the presence of joint inflammation or fluid build-up around the heart or lungs and to rule out other conditions, such as fractures, tumors, infection, or congenital defects
- Eye exam – to detect the development of eye inflammation
- EKG – to detect inflammation of the heart