Antibodies are proteins that are made as part of an immune response. Normally, the immune system responds to an infection by producing antibodies to fight bacteria or viruses. However, when a person has an autoimmune disease, the immune system malfunctions and may produce potentially harmful antibodies directed against one’s own body. These self-directed antibodies are referred to as autoantibodies. Autoantibody-mediated inflammation and cell destruction may affect blood cells, skin, joints, kidneys, lungs, nervous system, and other organs of the body. The Antinuclear Antibody (ANA) test identifies autoantibodies that target substances contained inside our own cells and are commonly found in autoimmune disorders. A positive test for ANA may help the doctor in establishing the diagnosis of an autoimmune disease as well as to determine the specific type. A negative test for ANA decreases the likelihood that a patient’s symptoms may be caused by an autoimmune disease. However, a positive test for ANA DOES NOT, BY ITSELF, INDICATE THE PRESENCE OF AN AUTOIMMUNE DISORDER. A significant percentage of asymptomatic people have positive test for ANA. Because of the design of the ANA test, many normal individuals will have a positive test at low titers. Even when detected at high titer, in absence of suggestive symptoms or positive clinical findings, a positive ANA result does not preclude that a patient either has, or will develop, an autoimmune disease.
A positive test for ANA always requires of expertise to weight the clinical significance depending on the patient’s symptoms or findings on physical examination.