Medical Definition of Antinuclear antibody
Antinuclear antibody: An unusual antibody that is directed against structures within the nucleus of the cell. Antinuclear antibodies (ANAs) are found in patients whose immune system is predisposed to cause inflammation against their own body tissues. Antibodies that are directed against one's own tissues are referred to as autoantibodies. The propensity for the immune system to work against its own body is referred to as autoimmunity. ANAs indicate the possible presence of autoimmunity.
The fluorescent antinuclear antibody test (FANA) was designed by George Friou, M.D. in 1957. It is done on a blood sample. The antibodies in the serum of the blood are exposed in the laboratory to cells and then one determines whether or not antibodies are present that react with various parts of the nucleus of the cell. It is a sensitive screening test used to detect autoimmune diseases.
Autoimmune diseases are conditions characterized by a disorder of the immune system featured by the abnormal production of antibodies (autoantibodies) directed against the tissues of the body. Autoimmune diseases typically feature inflammation of various tissues of the body. ANAs are found in patients with a number of autoimmune diseases, such as systemic lupus erythematosus, Sjögren syndrome, rheumatoid arthritis, polymyositis, scleroderma, Hashimoto thyroiditis, juvenile diabetes mellitus, Addison disease, vitiligo, pernicious anemia, glomerulonephritis, and pulmonary fibrosis. ANAs can also be found in patients with chronic infections and cancer. Many medications can stimulate the production of ANAs.
ANAs present different patterns depending on the staining of the cell nucleus in the laboratory: homogeneous, or diffuse; speckled; nucleolar; and peripheral or rim. While these patterns are not specific for any one illness, certain illnesses can more frequently be associated with one pattern or another. For example, the nucleolar pattern is more commonly seen in the disease scleroderma. The speckled pattern is seen in many conditions and in persons who do not have any autoimmune disease.
ANAs are present in approximately 5% of the normal population, usually in low titers (low levels). These persons have no disease. Titers of lower than 1:80 are less likely to be significant. Even higher titers are insignificant with aging over age 60 years. Ultimately, the ANA result must be interpreted in the specific context of the symptoms and other test results for the patient. It may or may not be significant in an individual.
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