Antinuclear antibodies 1:40
The body's immune system normally attacks and destroys foreign substances such as bacteria and viruses. However, in disorders known as autoimmune diseases, the immune system attacks and destroys the body's normal tissues. When a person has an autoimmune disease, the immune system produces antibodies that attacks the body's own cells as though they were foreign substances, often causing them to be damaged or destroyed. A test for antinuclear antibodies (ANA) is done to help diagnose conditions that include: • Systemic lupus erythematosus (SLE). Normal values of ANA vary from lab to lab.
Generally, titers of 1:40 and below are not considered significant. A high ANA titer may indicate systemic lupus erythematosus (SLE). SLE can be present with titers from 1 to 40 and higher. Almost all people with SLE have a high ANA titer. However, most people with a high ANA titer do not have SLE. Only about one-third of people who are referred to a rheumatologist for high ANA titers are diagnosed with SLE. Other conditions may cause a high ANA titer. About 30% to 40% of people with rheumatoid arthritis have a high ANA titer. Many conditions may result in a high ANA titer. These conditions include autoimmune diseases, such as scleroderma, Sjögren's syndrome, juvenile rheumatoid arthritis, and myositis. Other conditions with a high ANA titer include Raynaud's syndrome, viral infections, and liver disease. Although an ANA titer may help support a diagnosis for these conditions, it is not used by itself to confirm a diagnosis. A thorough medical history, physical examination, and other tests are needed to confirm a suspected autoimmune disease. Some healthy individuals have high levels of antinuclear antibodies. For instance, some people with a family history of autoimmune disease may have a high ANA titer. The higher the titer, however, the more likely it is that the person has an autoimmune disease. Factors that can interfere with your test and the accuracy of the results include: Medications, such as hydralazine (Apresoline), procainamide (Procan, Pronestyl, Promine), and certain anticonvulsants (such as Dilantin, Mysoline). These medications can cause a form of systemic lupus erythematosus (SLE) called drug-induced lupus. Lupus resulting from these medications may cause a high antinuclear antibody (ANA) titer. Other medications that can cause a similar problem are antibiotics (isoniazid, penicillin, and tetracycline), birth control pills, lithium, and some diuretics, such as chlorthalidone (Hygroton), and heart or blood pressure medications, such as acebutolol (Sectral), captopril (Capoten), atenolol (Tenormin), metoprolol (Lopressor), lovastatin (Mevacor), and quinidine. Some older adults (5% to 40%) may have mildly elevated levels. Older women appear to have higher ANA titers than older men. The result of an antinuclear antibody (ANA) test is used along with a thorough medical history, physical examination, and other tests to diagnose systemic lupus erythematosus (SLE) or other autoimmune diseases. SLE should not be diagnosed by the results of the ANA test alone.
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