Why should children undergo testing for the three rheumatism tests?

In general, testing for the three rheumatism-related markers in children is primarily used to determine the presence of related diseases. These three markers include rheumatoid factor (RF), anti-streptolysin O (ASO), and C-reactive protein (CRP). Specific details are as follows:

1. Rheumatoid Factor (RF)

Rheumatoid factor is an autoantibody produced in peripheral lymph nodes, synovial membranes of joints, tonsillar lymphoid follicles, and bone marrow. The positivity rate of RF in rheumatoid arthritis is about 80%, but it is not the sole diagnostic criterion for rheumatoid arthritis. This is because RF is not a specific antibody exclusive to rheumatoid arthritis and can also appear in various other conditions. In autoimmune diseases such as Sjögren's syndrome, RF is positive in approximately 50% of cases; in systemic lupus erythematosus, RF is positive in about 30%. Additionally, RF may frequently test positive in other autoimmune disorders such as scleroderma and dermatomyositis.

2. Anti-Streptolysin O (ASO)

This marker is used to detect streptococcal infection. Pyogenic streptococcal infections can cause pharyngitis, tonsillitis, pulmonary infections, endocarditis, and skin or soft tissue infections, and may even lead to systemic infection. Furthermore, this bacterium is an indirect cause of allergic or reactive diseases such as rheumatic fever and acute glomerulonephritis. Fever and arthritis are the most common symptoms of rheumatic fever. When rheumatic fever is suspected, ASO should be tested. A positive result indicates prior streptococcal infection.

3. C-Reactive Protein (CRP)

CRP is a protein produced by the body in response to tissue injury and acute inflammatory reactions, serving as an indicator of inflammatory status. For example, in infectious diseases such as pneumonia or bronchitis, CRP levels may significantly increase. It can also rise during non-infectious inflammatory conditions, such as rheumatic diseases. In various inflammatory joint diseases, including rheumatoid arthritis, CRP elevation is common. When assessing disease activity, CRP serves as a highly valuable objective marker, often more sensitive than subjective clinical symptoms and physical signs.

In summary, if a child presents with any of the aforementioned diseases or similar symptoms, testing for these three rheumatism-related markers may be necessary. It is important to undergo testing at a reputable medical institution to ensure accurate and reliable results.