Tuberculosis Skin Test
What is a skin test?
A skin test is a simple test, often called a Mantoux skin test, or tuberculin skin test (TST), done to find out if you have been infected with the tuberculosis (TB) bacteria. You cannot get TB from having the skin test done.
Who should be tested?
You should be tested if you:
- have been in contact with a person who has infectious TB disease,
- are going to live in a long-term care home,
- are starting work in a health care facility, day nursery, or long-term care home, and are required by your employer to have pre-employment or annual testing,
- are starting college or university in a health care program,
- have travelled to countries with a high prevalence of TB disease,
- are an intravenous (IV) drug user, or
- have a medical condition that increases the risk for TB disease, e.g. HIV, diabetes.
Do I need more than one skin test?
If you need yearly skin testing, you may be asked to have the skin test repeated one to three weeks later. This is called a "two-step" skin test, and is required only once in a person's lifetime. It is a more accurate way to determine if you have been infected in the past. Be sure to keep documentation of your test so you don't need to have a "two-step" skin test repeated.
If you are a contact of a case of infectious TB you will need to have the skin test repeated 8 weeks after your last exposure to the infected person.
How is the skin test done?
A small amount of the test liquid is placed by needle just under the skin of the forearm. This makes a little bump that goes away quickly. Two or three days later, the same doctor or nurse who gave you the test should look at your arm. If nothing is there, the test is negative. If there is swelling, the doctor or nurse will measure it and decide if the test is positive. The result is then recorded. It is important that you return to have your arm looked at, even if you feel nothing is there.
What if I have a positive skin test?
A positive skin test result means you may have been infected with the TB bacteria or other similar bacteria.
You will need to see your doctor to determine if you have latent or active TB disease. He or she will take a medical history and perform a physical exam. You will be sent for a chest x-ray. You may be asked to start medication to prevent TB disease.
Remember: a positive skin test means you have a small (5 to 10 percent) risk of developing TB disease in your lifetime.
If you are healthy, (i.e. no symptoms of persistent cough, fever, fatigue, night sweats, loss of appetite, or weight loss) you are unlikely to have TB disease or be infectious. A positive skin test does not mean you have active TB disease.
What are the possible side effects of the skin test?
The test area of your arm may be itchy and sore for a while if you have a very strong positive reaction. In rare cases, the skin may break down where the test was done or leave a scar.
Where can I have the test done?
You can have the test done at your doctor's office or some walk-in clinics. KFL&A Public Health only does TB skin tests for contacts of an active case of TB disease.
How can I get more information?
If you have any questions, please call the Communicable Disease team at 613-549-1232 or
1-800-267-7875, ext. 1287, or visit our website at www.kflapublichealth.ca.
Revised: 2013-02-25