What is the role of rheumatoid factors (RFs) in the diagnosis of rheumatoid arthritis (RA)?

Updated: Jan 28, 2021
  • Author: Tyler Street, MD; Chief Editor: Eric B Staros, MD  more...
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Immunoglobulin M (IgM) autoantibodies against the Fc fragment of immunoglobulin G (IgG) are called rheumatoid factors (RFs). These proteins are produced by B cells and can be found circulating in the blood. Their role is unknown in both healthy individuals and in those with rheumatoid arthritis. Approximately 60-80% of individuals with rheumatoid arthritis (RA) have RF present during the course of their disease. However, RF results are positive in less than 40% of patients with early RA. RF levels vary based on disease activity, though even patients with drug-induced remissions generally retain high titers of RF.

A study by Mouterde et al indicated that in patients with early arthritis, the disease demonstrates, in those who are seronegative for rheumatoid factor (RF) and anti–citrullinated protein autoantibodies (ACPAs), less activity at baseline and, at 3-year follow-up, less radiographic progression than it does in seropositive patients. [9]

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