Rheumatoid Factor
Rheumatoid factor (RF) is the auto
antibody that means, antibody directed against an organism's own
tissues. It is most relevant in rheumatoid arthritis. It is defined
as an antibody against the Fc portion of Ig G. RF and Ig G join to
form immune complexes that contribute to the disease process.
Antibodies are normally present in our body. It plays important role
in our immune system. This RF factor is not present in the normal
individual.
Rheumatoid factor can also be a cryo globulin (antibody that
precipitates on cooling of a blood sample); it can be either type 2
(monoclonal IgM to polyclonal IgG) or type 3 (polyclonal IgM to
polyclonal IgG) .
The presence of rheumatoid factor in serum can also indicate the
occurrence of suspected autoimmune activity unrelated to rheumatoid
arthritis, such as that associated with tissue or organ rejection. In
such instances, RF may serve as one of several serological markers
for autoimmunity.
Rheumatoid factor test
Rheumatoid factor is commonly used as a blood test for the
diagnosis of rheumatoid arthritis. Rheumatoid factor is present in
about 80% of adults (but a much lower proportion of children) with
rheumatoid arthritis.
Can rheumatoid factor be present in a patient without rheumatoid arthritis?
Yes. Rheumatoid factor is also present in patients with other
conditions, including other connective tissue diseases (such as
systemic lupus erythematosus), some infectious diseases (such as
infectious hepatitis, syphilis, infectious mononucleosis, parasites,
and tuberculosis), liver disease, and sarcoidosis. Rheumatoid factor
can also sometimes be present in normal individuals without diseases.
This occurs more frequently in people with family members who have
rheumatoid arthritis.
Results
High levels of rheumatoid factor (in general, above 20 IU/mL,
1:40, or over the 95th percentile; there is some variation among
labs) occur in rheumatoid arthritis .The higher the level of RF have
the probability of destructive articular disease. It is also found
in Epstein-Barr virus or Parvo virus infection and in 5-10% of
healthy persons, especially the elderly.
Rheumatoid factor may also be elevated in: chronic hepatitis,
primary biliary cirrhosis, any chronic viral infection, bacterial
endocarditis, leukemia, dermatomyositis, infectious mononucleosis,
systemic sclerosis, and systemic lupus erythematosus.
