Anti-nuclear Antibody Testing (ANA) is a blood test that looks for certain kinds of antibodies in the body. ANA tests are often used to help diagnose autoimmune diseases, such as systemic lupus erythematosus, Sjogren's syndrome and mixed connective tissue disease.
Normally, the immune system makes antibodies that recognize normal proteins inside cells. However, in some people, these antibodies can mistakenly attack the nucleus of a cell and cause a serious autoimmune disease, such as lupus or Sjogren's syndrome. The most common symptom that is related to an autoimmune disease is joint pain or swelling. Other symptoms can include fever, chills, nasal and oral ulcers, hair loss, severe dry eyes or dry mouth, and kidney disease. Most people who have lupus or other autoimmune conditions also have positive anti-nuclear antibody testing results. Other people with autoimmune diseases may have negative anti-nuclear antibody testing results, even though they have other symptoms and signs of an autoimmune condition. A person who has a positive Anti-nuclear Antibody Testing may have other symptoms of an autoimmune disease, such as rashes or blisters on the skin, swollen joints or tender muscles, and a general feeling of being run down. These symptoms could be due to any number of different autoimmune disorders, so it is important that the doctor carefully examine patient’s medical history and physical findings in order to accurately diagnose an autoimmune disorder. Typically, an ANA test is done in combination with other laboratory tests that look for specific autoantibodies and substances. These other tests are usually ordered if patients have a positive ANA and the doctor is still uncertain which autoimmune disease may be causing their symptoms. In the laboratory, professionals test the serum for antinuclear antibodies with a technique known as immunofluorescence. In this method, a fluorescent-labeled immunoglobulin made against nuclear components is used and then it is used for detecting the antibodies in the serum. The ANA antibody is then diluted with several dilutions of the normal saline until it is at a titer, which tells us how many ANA antibodies are present in the blood. When the titer is high, this means that the immune system has mounted a strong reaction against nuclear proteins. The titer tells how many anti-nuclear antibodies are present in the sample. A positive titer means there are more than a certain number of autoantibodies. This can help the doctor determine the onset of the autoimmune condition, how quickly it begins, and what type of symptoms are associated with it. If the titer is low, this indicates that there are only a few ANA antibodies in your blood. This is a normal reaction that occurs when cells are turning over in the body and the contents of the nuclear compartments are being revealed to the immune system for brief periods of time. This type of Anti-nuclear Antibody Testing is most effective in diagnosing autoimmune diseases like systemic lupus erythematosus, however, can also be used to detect other autoimmune disorders. The most common autoimmune diseases that can be tested for with ANA are lupus, Sjogren's syndrome and systemic sclerosis. In the laboratory, professionals measure patient’s ANA titer by setting up various dilutions of their sample and then looking for fluorescence on the antibody. They do this by incubating the diluted serum with rat liver and observing the fluorescence of the ANA antibodies that are bound to the rat liver.
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