A way to find out if you have TB germs in your body.
The tuberculosis (TB) blood test, also called an Interferon Gamma Release Assay or IGRA, is a way to find out if you have TB germs in your body. The TB blood test can be done instead of a TB skin test (Mantoux). A “positive” TB blood test result means you probably have TB germs in your body. Most people with a positive TB blood test have latent TB infection. To be sure, your doctor will examine you and do a chest x-ray. You may need other tests to see if you have latent TB infection or active TB disease 1 Positive IGRA: This means that the person has been infected with TB bacteria. 2  Additional tests are needed to determine if the person has latent TB infection or TB disease. 3  A health care worker will then provide treatment as needed. If a person does not have TB disease, but has TB bacteria in the body, then latent TB infection is diagnosed. The decision about treatment for latent TB infection will be based on a person’s chances of developing TB disease. 1 A negative test does not always mean that a person is free of tuberculosis. 2  A person who received a BCG vaccine (administered in some countries but not the U.S.) against tuberculosis may also have a positive skin reaction to the TB test. 1 Skin tests should be read 48-72 hours after the injection. 2  The basis of the reading of the skin test is the presence or absence and the amount of induration (localized swelling). 3  A tuberculin skin test (also called a Mantoux tuberculin test) is done to see if you have ever been exposed to tuberculosis (TB). The test is done by putting a small amount of TB protein (antigens) under the top layer of skin on your inner forearm. If you have ever been exposed to the TB bacteria (Mycobacterium tuberculosis), your skin will react to the antigens by developing a firm red bump at the site within 2 days. The TB antigens used in a tuberculin skin test are called purified protein derivative (PPD). Tuberculosis, MTB, or TB (short for tubercle bacillus), in the past also called phthisis, phthisis pulmonalis, or consumption, is a widespread, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. The classic symptoms of active TB infection are a chronic cough with blood-tinged sputum, fever, night sweats, and weight loss (the last of these giving rise to the formerly common term for the disease, consumption). Infection of other organs causes a wide range of symptoms. Testing & Diagnosis. Tuberculosis (TB) is a disease that is spread through the air from one person to another. There are two kinds of tests that are used to determine if a person has been infected with TB bacteria: the tuberculin skin test and TB blood tests. If a person does not have TB disease, but has TB bacteria in the body, then latent TB infection is diagnosed. The decision about treatment for latent TB infection will be based on a person’s chances of developing TB disease. A positive TB skin test or TB blood test only tells that a person has been infected with TB bacteria. It does not tell whether the person has latent TB infection (LTBI) or has progressed to TB disease. Other tests, such as a chest x-ray and a sample of sputum, are needed to see whether the person has TB disease. If a person does not have TB disease, but has TB bacteria in the body, then latent TB infection is diagnosed. The decision about treatment for latent TB infection will be based on a person’s chances of developing TB disease. Before having a tuberculin skin test, tell your doctor if you: 1  Have symptoms of tuberculosis (TB), such as an ongoing cough, night sweats, or unexplained weight loss. 2  Have had a severe reaction to a tuberculin skin test in the past. 3  Have had TB in the past. If you have ever been exposed to the TB bacteria (Mycobacterium tuberculosis), your skin will react to the antigens by developing a firm red bump at the site within 2 days. The TB antigens used in a tuberculin skin test are called purified protein derivative (PPD).
http://www.health.state.mn.us/divs/idepc/diseases/tb/factsheets/igra.html http://www.cdc.gov/tb/topic/testing/default.htm http://www.medicinenet.com/tuberculosis_skin_test_ppd_skin_test/article.htm http://www.webmd.com/a-to-z-guides/tuberculin-skin-tests https://en.wikipedia.org/wiki/Tuberculosis http://www.cdc.gov/tb/topic/testing/default.htm http://www.cdc.gov/tb/topic/testing/default.htm http://www.webmd.com/a-to-z-guides/tuberculin-skin-tests
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