Rheumatoid factor

Rheumatoid factor is an autoantibody directed against the Fc fragment of IgG's own immunoglobulins. The rheumatoid factor itself can be of the IgM, IgG, IgA, IgE and IgD classes. Commonly used nephelometry preferentially detects rheumatoid factor in the IgM class, enzyme immunoassay allows to determine a specific class. It is used primarily in the diagnosis of Rheumatoid Arthritis, elevated levels may be in some other conditions or in healthy individuals.