Medical Q&As

Rheumatoid factor - what is it?

What is rheumatoid factor? Is it a kind of debris in the blood or what? What does a high rheumatoid factor in a person with rheumatoid arthritis mean exactly?

Rheumatoid factor is an antibody that is present in the blood of over 80% of people with rheumatoid arthritis. The test is mainly used in the diagnosis of rheumatoid arthritis and a high level of rheumatoid factor is usually indicative of an aggressive form of the disease. Rheumatoid arthritis is a form of autoimmune disease, which means that the body’s immune system reacts against various structures within the body rather than the more usual stance of defending the body against external threat. The presence of the antibody is not always diagnostic of rheumatoid arthritis. It can also be present with other diseases such as SLE (systemic lupus erythematosus), scleroderma and chronic viral infection. Therefore the significance of a positive test result has to be interpreted in the light of other test results and the patients’ symptoms and physical signs.