Tuberculosis - TB Test

This test is used to determine if you have been infected with tuberculosis.

This test is used to determine if you have been infected with tuberculosis.

This test checks to see if you have been infected with tuberculosis.

  • Tuberculosis is a contagious bacterial infection. Once a person has been infected it can spread from the lungs to other parts of the body.
  • People who have active tuberculosis can spread it to others when they cough.
  • Most people with a positive TB skin test have been previously exposed to the TB bacteria. However, they do not have an active TB infection.

For this test, a needle is used to inject a small amount of fluid just under the skin's surface. If a palpable, raised hardened area (bump) appears over the next few days, the test is considered positive. The reaction should be measured by the size of the bump (in millimeters) and not the size or presence of redness around the injection site.

  • A positive test means you have been, exposed to tuberculosis and will need additional testing to find out if you are actively infected. Most people with a positive test are not actively infected.
  • You may be asked to go back to your healthcare provider's office in 48 to 72 hours to have the injection area checked again.
  • An older prong test, called a tine test, was previously used to screen for TB. Although this test was easy to do, it was not very accurate and should no longer be used.

Tell your healthcare provider if you:

  • Have had a positive TB test in the past
  • Take medications that affect your immune system, such as steroids
  • Have previously received a vaccine for tuberculosis (BCG vaccine) - this will make a TB skin test positive.

Your medical history may be important in determining how the test result is interpreted.

What should I ask my healthcare provider before having this test?

  • Is there any special preparation for the test? (If so, get clear instructions on what you need to do.)
  • What is the reason for the test? Will the test results change my treatment plan? If not, do I need the test?


Also known as:

Tuberculosis Testing
Tuberculosis Test Reading
Tuberculosis Skin Test
Tuberculosis - TB Test
TB Testing
TB Test Reading
TB Screening
PPD Test
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