Tuberculosis Skin Testing – What you need to know!

by Kristin Gagnon, RN

Tuberculosis Skin Testing – What you need to know!

by Kristin Gagnon, RN

by Kristin Gagnon, RN

Congratulations! You’ve been accepted to that school program or perhaps you got that new job. But before you can start you’ve been asked to complete a TB skin test by your school or employer. No idea what a TB skin test is? Here’s what you need to know.

What is TB?

TB, or tuberculosis, is a bacteria spread through the air when a contagious person coughs, sneezes, sings or talks. TB usually occurs in the lungs but can affect any organ. Medication is available to treat TB.

What is a TB skin test?

The TB skin test is used to detect infection with TB bacteria. The TB test consists of two appointments:

Appointment #1: A small amount (0.1mL) of test substance is injected under the first layer of skin on your forearm. If you have been exposed to TB bacteria your skin will react to form a firm red bump.

Appointment #2: You must return to the clinic 48 to 72hrs later to have your forearm looked at by the nurse. If it is not looked at within 72 hours the result becomes invalid and the test must be repeated. Make sure to arrive on time for your second appointment!

What is a two-step TB skin test?

If you have been asked for a two-step TB test then you need to repeat the exact same procedure 1-3 weeks after the first test. A two-step TB test is used to establish a baseline for people who need regular TB skin testing.

Is there anything I need to do to get ready for the test?

  • Be sure you don’t receive any live vaccines in the 28 days before your TB test as they can interfere with the test (MMR, chicken pox, oral typhoid, shingles, or yellow fever vaccines). These vaccines can be given on the same day as the TB test or anytime after the test is completed. Td, Tdap, polio, hepatitis A and B are all inactivated vaccines and can be given anytime before or after the TB test.
  • If you need other vaccines please bring your list for the nurse to review and any forms you may need signed.
  • Please bring a list of your current medications.

Is there anything I can’t do after the TB test?

DO everything as you normally would. Eat and drink as normal. Shower and swim as much as you like.

DON’T scratch it or put a bandage on it (in case the bandage irritates your skin). If it becomes itchy you can put a cool cloth on it. Do not put any creams on it.

I’ve had the BCG vaccine – Can I still get a TB test?

Yes you can! The BCG vaccine, or Bacille Calmette Guerin, is routinely given in many countries to protect against TB disease. Although there is a chance the BCG vaccine may cause a false-positive TB skin test, this is not likely if you received the vaccine more than 10 years ago.

My TB skin test is positive – does this mean I have TB?

Not necessarily! The TB test can be positive if you have been infected with TB bacteria, had a previous BCG vaccine, or have had an infection with non-TB bacteria from the same family of bacteria. The test cannot determine how long you may have been infected with TB or whether the bacteria is active or latent (sleeping). The next step is to review your health history with the nurse and complete a chest x-ray to see if TB bacteria are growing in your lungs.

What’s the difference between active and latent TB?

  • Latent TB infection occurs when you have breathed in the TB bacteria but your immune system stops the bacteria from multiplying so you don’t get sick. If you have latent TB you don’t have any symptoms and cannot spread TB to other people.
  • Active TB disease occurs when you have breathed in the TB bacteria but your immune system does not stop the bacteria from multiplying. These multiplying bacteria can make you very sick.

Where can I get the x-ray done?

You can go to any hospital in the Lower Mainland for your x-ray (eg. St Paul’s Hospital, Vancouver General Hospital, Royal Columbian Hospital, Burnaby General Hospital). Take your requisition to the radiology department. The x-ray is free when you have a BC care card.

How do I get the results?

A doctor at TB Control will review your health history and look at your x-ray. An x-ray report will be mailed to your home address if no further follow-up is required. It can take 4-6 weeks to receive your x-ray results in the mail. If you have still not received your results after this time please call TB control (TravelSafe clinic does not receive any x-ray results).


TB Control Vancouver Clinic
655 West 12th Avenue
Vancouver, BC V5Z 4R4
Phone: 604-707-2692

TB Control New Westminster Clinic
100-237 Columbia Street E
New Westminster, BC V3L 3W4
Phone: 604-707-2698


Please see the following links for further information on Tuberculosis in Chinese, Korean, Punjabi and French.


Be sure to get your TB test as soon as you find out you are accepted into your school program or got your new job. Whenever possible don’t leave it to the last minute!

Any other questions you may have can be answered by the nurse at the TravelSafeTM clinic when you come in for your TB test. See you soon!

Before you travel, protect your health.

TravelSafely with TravelSafe Immunization Clinic