Tuberculosis Facts
Testing for TB
What is TB?
TB is short for a disease called tuberculosis. TB is spread
through the air from one person to another. TB germs are passed
through the air when someone who is sick with TB disease of the
lungs or throat coughs, speaks, laughs, sings, or sneezes. Anyone
near the sick person can breathe TB germs into their lungs.
TB germs can live in your body without making you sick. This is
called latent TB infection. This means you have only inactive
(sleeping) TB germs in your body. The inactive germs cannot be
passed on to anyone else. However, if these germs wake up or become
active in your body and multiply, you will get sick with TB disease.
When TB germs are active (multiplying in your body), this is
called TB disease. These germs usually attack the lungs. They can
also attack other parts of the body, such as, the kidneys, brain, or
spine. TB disease will make you sick. People with TB disease may
spread the germs to people they spend time with every day.
How do I know if I have been infected with TB germs?
If you have been around someone who has TB disease, you should go
to your doctor or your local health
department for tests.
There are two tests that can be used to help detect TB
infection: a skin test or a special TB blood test. The skin
test is used most often. A small needle is used to put some
testing material, called tuberculin, under the skin. In 2-3
days, you return to the health care worker who will check
to see if there is a reaction to the test. In some cases, a
special TB blood test is given to test for TB infection. This
blood test measures how a person’s immune system reacts
to the germs that cause TB.
To tell if someone has TB disease, other tests such as chest
x-ray and a sample of sputum (phlegm that
is coughed up from deep in the lungs) may be needed.
Note: If you have ever had a “positive” reaction to a TB skin
test or if you have been treated with TB drugs in the past, tell your
health care worker.
Last Modified: 10/7/2008
Last Reviewed: 05/18/2008 Content Source: Division of Tuberculosis Elimination
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
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