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, 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. Studies from as early as 1984 suggest that the detection of RF IgA in early disease indicates poor prognosis and justifies a more aggressive course of treatment. 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.
Reported (Analytical Time)
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