Tuberculosis (TB)


How can I get tested for TB?

You should get tested for TB if:

  • You have spent time with a person known to have active TB disease or suspected to have active TB disease; or

  • You have HIV infection or another condition that puts you at high risk for active TB disease; or

  • You think you might have active TB disease; or

  • You are from a country where active TB disease is very common (most countries in Latin America and the Caribbean, Africa, Asia, Eastern Europe, and Russia); or

  • You live somewhere in the United States that active TB disease is more common such as a homeless shelter, migrant farm camp, prison or jail, and some nursing homes); or

  • You inject illegal drugs.

The TB skin test

The TB skin test may be used to find out if you have TB infection. You can get a skin test at the health department or at your doctor's office. A health care worker will inject a small amount of testing fluid (called tuberculin or PPD) just under the skin on the under side of the forearm. After 2 or 3 days, you must return to have your skin test read by the health care worker. You may have a swelling where the tuberculin was injected. The health care worker will measure this swelling and tell you if your reaction to the test is positive or negative. A positive reaction usually means that you have been infected by someone with active TB disease.

If you have recently spent time with and been exposed to someone with active TB disease, your TB skin test reaction may not be positive yet. You may need a second skin test 8 to 10 weeks after the last time you spent time with the person. This is because it can take several weeks after infection for your immune system to react to the TB skin test. If your reaction to the second test is negative, you probably do not have latent TB infection.

QuantiFERON®-TB Gold

QuantiFERON®-TB Gold (QFT) is a blood test used to find out if you are infected with TB bacteria. The QFT measures the response to TB proteins when they are mixed with a small amount of blood. Currently, few health departments offer the QFT.

If your health department does offer the QFT, only one visit is required, at which time your blood is drawn for the test.

What if I have a positive test for TB?

If you have a positive reaction to the TB skin test or the QFT, your doctor or nurse may do other tests to see if you have active TB disease. These tests usually include a chest x-ray and a test of the phlegm you cough up. Because the TB bacteria may be found somewhere other than your lungs, your doctor or nurse may check your blood or urine, or do other tests. If you have active TB disease, you will need to take medicine to cure the disease.

What if I have been vaccinated with BCG?

BCG is a vaccine for TB. This vaccine is not widely used in the United States, but it is often given to infants and small children in other countries where TB is common. BCG vaccine does not always protect people from getting TB.

If you were vaccinated with BCG, you may have a positive reaction to a TB skin test. This reaction may be due to the BCG vaccine itself or due to infection with the TB bacteria. Your positive reaction probably means you have been infected with TB bacteria if:

  • You recently spent time with a person who has active TB disease; or

  • You are from an area of the world where active TB disease is very common (such as most countries in Latin America and the Caribbean, Africa, Asia, Eastern Europe, and Russia); or

  • You spend time where TB disease is common (homeless shelters, migrant farm camps, drug-treatment centers, health care clinics, jails, prisons).

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Important disclaimer: The information on pkids.org is for educational purposes only and should not be considered to be medical advice. It is not meant to replace the advice of the physician who cares for your child. All medical advice and information should be considered to be incomplete without a physical exam, which is not possible without a visit to your doctor.


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