Rheumatoid factor IgG

General Information

Rheumatoid factor (RF) Is a heterogeneous group of autoantibodies to the body's own immunoglobulin that has changed its properties under the influence of a virus or other agent. They are usually IgM antibodies, but may also be IgG and IgA antibodies.

RF is synthesized by plasma cells of the synovial membrane. Autoantibodies can form immune complexes with both complement system proteins and other proteins. Upon entering the synovial fluid, autoantibodies are phagocytosed and destroyed by neutrophils, which induces the release of inflammatory mediators that damage joint tissue.

Autoantibodies can also form large protein complexes that fail to phagocytose and are therefore deposited around blood vessels in the intercellular space, leading to the development of an inflammatory reaction - vasculitis.

RF is not involved in initiating the inflammatory process that causes rheumatoid arthritis, although it is likely to contribute to the aggravation and persistence of the process.

RF may appear in the body before the onset of the disease and sometimes several years before the clinical manifestation of the disease.

According to the presence / absence of rheumatoid factor, rheumatoid arthritis is divided into 2 categories: seropositive or seronegative. The risk of developing erosive arthritis in seropositive patients with rheumatoid arthritis, with loss of joint function and external manifestations, is several times higher than in seronegative patients.

HIV-positive patients are at high risk of developing seronegative arthritis with loss of joint function and external manifestations such as rheumatoid nodules, lung disease, vasculitis, Felt syndrome (neutropenia and splenomegaly associated with rheumatoid arthritis).

RF is not specific for rheumatoid arthritis and is also defined in other connective tissue diseases and some chronic infections (endocarditis, tuberculosis, hepatitis B).

When should we take a test for rheumatoid factor?

• Rheumatoid arthritis;
• Differential diagnostics and prognosis of inflammatory diseases of the joints;
• Autoimmune diseases;
• Differential diagnostics of type II mixed cryoglobulinemia or Sjogren's syndrome, monitoring of the condition of patients with Sjogren's syndrome (disappearance of rheumatoid factor may indicate the development of lymphoma);
• Chronic inflammatory diseases.

How to prepare for the test?

The test should be performed on an empty stomach.

Research material

Venous blood

Possible interpretation of the results

RF level increases:

• Rheumatoid arthritis (usually high titer);
• Mixed cryoglobulinemia (in 70-100% of cases);
• Sjogren's syndrome (in 75-90% of cases);
• Mixed connective tissue diseases (in 50-60% of cases);
• Systemic lupus erythematosus (in 20-35% of cases);
• Scleroderma (in 20-30% of cases);
• Juvenile arthritis (in 15-25% of cases);
• Systemic vasculitis (in 5-20% of cases);
• Polymyositis (in 5-10% of cases);
• Hypersensitive vasculitis (in 5-15% of cases);
• Infections of various etiologies (subacute bacterial endocarditis, salmonellosis, brucellosis, tuberculosis, syphilis, measles, rubella, influenza, chronic hepatitis, parasitic infections);
• Lung diseases (sarcoidosis, interstitial fibrosis, silicosis, asbestosis);
• Primary biliary cirrhosis;
• Malignant neoplasms (especially leukemia and colon cancer).