The rheumatoid factor (RF) test is a critical diagnostic tool for rheumatoid arthritis (RA). Rheumatoid factor is an antibody present in the blood of many patients with RA, and the test measures its level. A positive RF test indicates a high level of rheumatoid factor in the blood, which is often associated with RA.
This test is part of a group of blood tests used to diagnose RA, which may include Anti-nuclear antibody (ANA), Anti-cyclic citrullinated peptide (anti-CCP) antibodies, C-reactive protein (CRP), and Erythrocyte sedimentation rate (ESR or sed rate). The RF test specifically looks for rheumatoid factor in a blood sample, a protein made by the immune system that can attack healthy cells.
Symptoms of RA, like pain, swelling, and stiff joints, often prompt the use of the RF blood test for diagnosis. The test measures the amount of RF in your blood, which is an autoantibody formed in people with RA. A positive rheumatoid factor blood test used to be a primary method for diagnosing RA, but now it’s understood that RF levels can also be high in other autoimmune diseases. Therefore, an RF test alone cannot conclusively diagnose RA.
Rheumatoid factor is part of the immune system’s attack on healthy tissues and cells, causing inflammation. Approximately 80% of adults with RA have rheumatoid factor, making it a common blood test during the diagnosis process. High levels of rheumatoid factor could help doctors make a diagnosis of RA, but as mentioned, it’s not solely definitive for RA.
For more detailed information, you can refer to the following sources:
RheumatoidArthritis.org on rheumatoid factor in RA diagnosis.
Mayo Clinic provides an overview of the RF test.
MedlinePlus on the RF test specifics.
WebMD discusses the RF test for RA diagnosis.
Verywell Health explains the RF blood test and its uses.
RheumatoidArthritis.org on various RA blood tests.
Medical News Today on RF ranges, tests, and treatment.
Verywell Health on RA blood tests for diagnosis.
Arthritis Foundation on testing for RA.
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