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�ٺ���Ƶ doctors can perform screening tests in people who may have been exposed to Mycobacterium tuberculosis, the bacterium that causes tuberculosis. Only a minority of those who come in contact with another person who has tuberculosis become infected. 

In the majority of those who become infected with tuberculosis-causing bacteria, the infection is latent, meaning the organism is not reproducing or causing disease. About 10 percent of people with a latent infection eventually develop tuberculosis. 

Screening tests for tuberculosis can help doctors identify people at risk for developing the condition. �ٺ���Ƶ doctors may recommend screening for people at high risk of becoming infected, and for those in whom the risk of progressing to disease would be high once infected—including those with certain medical conditions. This approach is called targeted testing. 

Doctors typically recommend screening for household contacts of people with tuberculosis, recent immigrants from countries where the disease is common, and people with HIV infection and other conditions that suppress the immune system.

�ٺ���Ƶ doctors may use a tuberculin skin test, in which a doctor injects a small amount of tuberculosis antigens into the skin of the forearm. Antigens are substances that trigger a response from the immune system. 

A doctor monitors the site over a period of 48 hours to see if the skin reacts. If a small bump forms, this indicates a person has been exposed to tuberculosis, but does not necessarily have the active form of the disease. Depending on your medical history and whether you have symptoms, doctors may recommend other diagnostic tests to evaluate you further. 

Doctors may also use a blood test called a quantiferon level to determine if you’ve been exposed to tuberculosis.