Rheumatoid factor - Definition

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A rheumatoid factor (RF) is an abnormal protein with autoantibody activity, meaning an antibody that reacts against the body's own cells. Research for the rheumatoid factor is conducted in cases of a suspected inflammatory rheumatic disease, rheumatoid arthritis. The presence of rheumatoid factor is not always the case, especially early in the disease, and other diseases such as chronic infections or other inflammatory diseases like Sjogren's disease, are associated with presence of this factor, which makes RF a convincing element in the diagnosis of rheumatoid arthritis, but not an absolute confirmation. Several blood tests can be used to identify it.