About Rheumatoid Factor
Rheumatoid factor (RF) is an antibody that attacks the Fc portion of IgG antibodies and is used as a diagnostic marker for rheumatoid arthritis (RA). Approximately 70–80% of people with RA are RF-positive, but RF also appears in other autoimmune diseases (Sjögren's, lupus), chronic infections, and in up to 10% of healthy older adults. Anti-CCP antibodies are now considered more specific for RA and are increasingly tested alongside RF to improve diagnostic accuracy.