What are rheumatoid factors (RFs)?

Updated: Jan 28, 2021
  • Author: Tyler Street, MD; Chief Editor: Eric B Staros, MD  more...
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Antibodies directed against the Fc fragment of immunoglobulin G (IgG) are called rheumatoid factors (RFs). They are heterogenous and usually composed of immunoglobulin M (IgM). Because of this, most assays detect only IgM. RFs are used as a marker in individuals with suspected rheumatoid arthritis (RA) or other autoimmune conditions. [1, 2, 3, 4, 5]

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