Heterogeneous
autoantibodies usually of the IgM class that react against the Fc region
of human IgG.
Normal Range: Negative (<1:16)
Positive
in: Rheumatoid arthritis (75-90%), Sjogren's (80-90%), scleroderma, dermatomyositis,
SLE (30%), sarcoidosis, Waldenstrom's macroglobulinemia. Drugs: methyldopa,
others. Low titer can be found in healthy older patients (20%). 1-4% of
normals and in a variety of acute immune responses (eg, viral infections,
infectious mononucleosis, and viral hepatitis), chronic infections (tuberculosis,
leprosy, subacute bacterial endocarditis) and chronic active hepatitis.
Additional: It can
be useful in differentiating rheumatoid arthritis from other chronic inflammatory
arthritides. However, a positive RF test is only one of several criteria
needed to make the diagnosis of rheumatoid arthritis.
