Rheumatoid arthritis (RA) is a chronic inflammatory disease affecting the joints. It is caused when lymphocytes in the synovial membranes produce abnormal IgG antibodies. Rheumatoid factors are autoantibodies of a patients own IgG and IgM that react with the Fc component of the abnormal synovial antigenic IgG to form immune complexes. These immune complexes activate the complement system and other inflammatory systems to cause joint damage.
Rheumatoid factor plays a role in diagnosis of RA and also can serve as a prognostic indicator. High RF concentrations have been associated with a more severe disease course.
Ambient (8 - 24 degrees Celsius)
High levels of rheumatoid factor are closely associated with autoimmune disease, particularly rheumatoid arthritis. But a number of other diseases and conditions can raise rheumatoid factor levels, including:
Inflammatory lung diseases, such as sarcoidosis
Mixed connective tissue disease
Systemic lupus erythematosus
Some healthy people (particularly older individuals) have positive rheumatoid factor tests, though it’s not clear why. And some people who have rheumatoid arthritis will have low levels of rheumatoid factor in their blood.
Reference Interval ≤16 IU/mL
N.B There is no available reference interval for aspirates, as this assay has not been formally validated for this sample type.
Nephelometric immunoassay on Siemens BNII nephelometer.
$21.82 (Exclusive of GST)
Measurement uncertainty 10 %
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