Monday, March 16, 2015

Rheumatoid Factor


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.

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