Rheumatoid factor in the blood
Last reviewed: 23.04.2024
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The reference values (norm) of concentration of rheumatoid factor in blood serum when determined by nephelometry are less than 14 IU / ml.
Rheumatoid factor - autoantibodies IgG, IgM, IgA or IgE classes, reacting with Fc-fragment IgG. It is formed as a result of stimulation with aggregated modified IgG or due to the action of exogenous cross-reactive antigen in violation of immunoregulation. Complex IgG + rheumatoid factor is not phagocytosed, deposited in the perivascular space, stimulating cell-mediated cytotoxic reactions, which leads to inflammation.
An increase in the concentration of rheumatoid factor in the blood is characteristic for rheumatoid arthritis (up to 90% of patients); the dependence of the titer of the rheumatoid factor on the duration of the disease was not revealed. The detection of rheumatoid factor in the presence of an appropriate clinical picture confirms the diagnosis of rheumatoid arthritis, but its seronegative forms are possible. An increase in the titer of the rheumatoid factor is determined not earlier than 6-8 weeks after clinical manifestations. The negative result of the study does not always allow to exclude the diagnosis. The presence of rheumatoid factor in patients with established diagnosis of rheumatoid arthritis indicates a severe form of the disease (occurs with a pronounced inflammatory process in the joints, often with their destruction). Rheumatoid factor can be detected in low titres for infectious mononucleosis, acute inflammatory processes, systemic lupus erythematosus with joint damage, Sjogren's syndrome, sarcoidosis, hepatitis.
An increase in the concentration of rheumatoid factor is possible with Felty's syndrome - a special form of rheumatoid arthritis characterized by leukopenia and acute onset; with the syndrome of Still (test is positive in 20% of cases) - a youthful form of rheumatoid arthritis, which clinically proceeds as Felty syndrome, but unlike it is accompanied by leukocytosis.
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