Laboratory examination of health, Rheumatoid Factor

Rheumatoid factor (rheumatoid factor, RF) are immunoglobulins that react with IgG molecules. Because the patient also contain IgG in serum, then the RF including autoantibodies. RF causative factor is not known for sure, although complement activation due to the interaction of RF with IgG play an important role in rheumatoid arthritis (rheumatoid arthritis, RA) and other diseases with positive RF. Most of the RF is IgM, but can also be IgG or IgA.

Positive RF was found in 80% of patients with rheumatoid arthritis. Very high RF levels indicate a poor prognosis with severe joint disorders and possible systemic complications.

RF often found in other autoimmune diseases, such as LE, scleroderma, dermatomyositis, but levels are usually lower than the levels of RF in rheumatoidarthritis. Low levels of RF are also found in non-immunological diseases and the elderly (above 65 years).

RF test is not used for monitoring treatment because the results of common tests remain positive, although there has been a clinical recovery. In addition, it takes about 6 months for a significant increase in titer. For the diagnosis and evaluation of RA is often used CRP test and ANA.

RF test for serum patients examined using the method of latex agglutination or nephelometry.

Reference Values

ADULT : a chronic inflammatory disease; 1/20-1/80 positive for the state of rheumatoid arthritis and other diseases;> 1 / 80 positive for rheumatoid arthritis.

CHILDREN : usually not done

Elderly : slightly increased

* Reference value may be different for each laboratory, depending on the method used.

Clinical Problems

INCREASED CONTENT : rheumatoid arthritis, LE, dermatomyositis, scleroderma, infectious mononucleosis, leukemia, tuberculosis, sarcoidosis, cirrhosis, hepatitis, syphilis, chronic infections, the elderly.

Factors that may affect the laboratory's findings :

• RF test results are often still found to be positive, regardless of whether there has been a clinical recovery.
• RF can be positive test results on a variety of clinical problems, such as collagen disease, cancer, cirrhosis of the liver.
• Elderly may have increased titers of RF, without suffering any illness.
• Due to diversity in the sensitivity and specificity of this screening test, positive findings should be interpreted based on the evidence contained in the clinical status of patients.