Tests
1st tests to order
CBC
Test
Typically normal in oligoarticular JIA. Children with systemic-onset juvenile idiopathic arthritis (SoJIA) often have anemia, thrombocytosis, and leukocytosis. Children with polyarticular and enthesitis-related JIA might have mild anemia and thrombocytosis.
Useful baseline test for all patients. Normal results do not exclude diagnosis.
Important to help exclude differentials such as infection or malignancy.
Result
normal or reduced hemoglobin and elevated platelets
erythrocyte sedimentation rate
Test
Elevated to varying levels in different subtypes. Significantly elevated in SoJIA; mildly to moderately elevated in polyarticular JIA; and may be normal or mildly elevated in oligoarticular JIA.
Nonspecific marker that may be elevated due to acute-phase responses from any cause.
Result
normal or elevated
C-reactive protein
Test
Elevated to varying levels in different subtypes.
Nonspecific marker that may be elevated due to acute-phase responses from any cause.
Result
normal or elevated
antinuclear antibodies (ANA)
Test
Positive in oligoarticular JIA and to a lesser extent in polyarticular JIA. ANA is generally negative in systemic and enthesitis-related subtypes.
ANA testing should be done as a baseline test. Positive ANA is associated with increased susceptibility to uveitis. Positive ANA alone is not diagnostic of JIA and negative ANA does not rule it out. False-positive ANA tests are frequent.
Result
positive or negative
rheumatoid factor (RF)
Test
Positive in RF-positive polyarticular JIA and negative in other subtypes. Two positive test results are required for diagnosis of RF-positive polyarticular JIA. Positive RF is associated with aggressive disease. Do not order RF to make a diagnosis of JIA. JIA is a clinical diagnosis and RF should only be ordered to prognosticate severity.[51]
Result
positive or negative
Tests to consider
anticyclic citrullinated peptide antibody
Test
Positive in rheumatoid factor (RF)-positive polyarticular JIA; negative in other subtypes. May be helpful in older children with polyarticular JIA who have negative tests for RF.
Result
positive or negative
chlamydia test
Test
May be indicated in teenage patients with monoarticular disease.
Result
positive if Chlamydia infection
ferritin levels
Test
Ferritin levels should be measured if SoJIA is suspected.
Result
may be abnormal
ultrasound of affected joints
Test
Often abnormal early in the course of disease. Useful in identifying joints for corticosteroid injection in oligoarthritis. Can be an important positive or negative finding if the diagnosis is questionable.
Has demonstrated higher sensitivity in assessing synovitis than clinical examination. However, further studies are needed to evaluate reliability and responsiveness in assessing synovitis changes on follow-up.[53]
Result
abnormal
MRI
Test
MRI may be indicated in patients with monoarticular disease to rule out other diagnoses such as pigmented villonodular synovitis or synovial hemangiomas. It can also be used to monitor cartilage injury.
Result
synovial fluid; synovial thickening and/or synovial enhancement
Use of this content is subject to our disclaimer