Rheumatoid Arthritis Test - Rheumatoid Factor (RF)
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About Our Rheumatoid Arthritis Test - Rheumatoid Factor (RF)
Note: Fasting is not required for this test.
Rheumatoid Factor (RF) is the autoantibody in rheumatoid arthritis (RA). An autoantibody is an antibody that is directed against an organism's own tissues (like in autoimmune diseases). In cases of rheumatoid arthritis, 4 out of 5 people will have RF detectable in their blood. This blood test examines RA Factor IgG, IgA, and IgM antibodies.
Rheumatoid factor can also be detected in individuals with other autoimmune disorders, not only rheumatoid arthritis.
The concentration of RF tends to be highest when the disease peaks and tends to decrease during prolonged remission. RF IgM is found in 1 to 4% of the general population. RF is present in 75% of adult RA patients with the highest incidence of RF occurring in persons over 65 years of age. Increased RF levels may also accompany a variety of acute immune responses, particularly viral infections and a number of other diseases (infectious mononucleosis, lyme disease, tuberculosis, leprosy, various parasitic diseases, liver disease, sarcoidosis, and systemic lupus erythematosus). In addition to RF IgM, raised levels of RF IgA and IgG have been reported in patients with RA. Recently, it has become apparent that the specificity and predictive value of the RF test is substantially increased by the detection of all three RF isotypes.