Which laboratory tests are recommended for confirming a diagnosis of JIA and ruling out other conditions?

Recommended laboratory tests for confirming juvenile idiopathic arthritis (JIA) and excluding other conditions include:

• Full blood count (FBC) to assess for anaemia or infection, which may mimic or complicate JIA ¹.
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) as markers of systemic inflammation, supporting the diagnosis of JIA but not specific to it ¹.
• Rheumatoid factor (RF) testing, which is positive in a minority of JIA cases and helps to classify subtypes but is not diagnostic alone ¹.
• Antinuclear antibody (ANA) testing, useful for identifying patients at risk of uveitis and supporting diagnosis, though not definitive ¹.
• Exclusion of infection or malignancy through relevant cultures or blood film if clinically indicated ¹.
• Additional tests such as HLA-B27 may be considered in cases with enthesitis-related arthritis features ¹.

These tests collectively help confirm JIA by demonstrating inflammation and excluding mimicking conditions such as infection, malignancy, or other rheumatological diseases. Recent pediatric rheumatology literature emphasizes the importance of a comprehensive panel including inflammatory markers, autoantibodies, and exclusion tests to improve diagnostic accuracy and guide management (Pilania and Singh, 2019).