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revised February 28, 2020

Arrow Bullet Tuberculosis (TB) and Skin Tests

What is Tuberculosis?

  • Tuberculosis (TB) is an infectious disease caused by the tuberculosis bacteria (germ). TB usually causes disease in the lungs, but may affect other parts of the body. TB is only contagious when diagnosed as active disease in the lungs or larynx. It is spread by coughing. Usually, close prolonged contact is required for transmission. Symptoms of TB include fatigue, fever, night sweats, weight loss, coughing, and chest pain. When someone has symptoms from TB, we say the person has active TB disease.

  • Tuberculosis is now preventable and curable with proper antibiotic treatment.

  • Only a small percentage of people exposed to the TB germ ever get active TB disease.
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Why Do I Need a Tuberculin Skin Test?

  • A TB skin test will show whether someone has been exposed to TB germs. A TB skin test is done for the following reasons: you are a contact of a person who has infectious TB disease, it is a requirement of employment or to determine past exposure as part of a medical assessment.
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What is a TB Skin Test?

  • TB skin test fluid contains a form of killed TB germs. A tiny amount of this test fluid is injected just under the skin of your forearm. This is not a vaccination. The skin test cannot give you tuberculosis. The skin test is able to detect TB antibodies.

  • The test site must be read within 48-72 hours to determine if the test is negative or positive. Only reactions of a certain size are considered significant.

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What Reaction Can I Expect at the Test Site?

  • There may be swelling or redness at the test site and slight discomfort such as itching.
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Does a Positive Skin Test Mean that I have Tuberculosis?

  • A positive skin test means that you have been exposed to the TB germ at sometime in your life. You have TB infection. It does not mean you have tuberculosis disease. You will be referred to your family doctor for assessment. A chest x-ray will be necessary to determine if the TB germs have done any damage to your lungs. Your doctor may prescribe medication to prevent TB.

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Additional Information

  • Pregnancy or history of previous BCG are not contraindications to receiving this test.

  • Keep a record of your TB skin test. A documented positive skin test is usually not repeated as the test will continue to react positive.

  • TB skin tests are not provided at Peel Sexual Health Clinics or by the TB program. Call your family doctor or walk - in clinic. Prices do vary so call around.

  • Peel Public Health - TB program does not provide training on TB skin testing to agencies. Skin testing training is offered through British Columbia Centres for Disease Control.
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  • Tuberculosis is contagious if active in the lungs or larynx.

  • A TB skin test can determine if you have been exposed to TB germs.

  • Medication is effective in preventing and curing tuberculosis.
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Revised: February 28, 2020

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