Understanding the TB Skin Test

The TB skin test, also known as the tuberculin skin test (TST) or Mantoux Test, is a simple and effective method to determine if you have ever been infected with tuberculosis.

How is the TST Performed?

To complete a TST, you will need to visit the travel health center at least twice. During your first visit, a nurse will inject a small amount of tuberculin solution into the skin on your forearm. After 48-72 hours, you will need to return for the nurse to check the injection site for any reactions, such as a raised, hard area or swelling.

Why Are Two-step (2-step) TST Needed?

Some countries, like Canada, may require 2-step TST as proof of testing. This is because a person's TST reaction may become less sensitive over time, leading to a false negative on the first test. The benefit of conducting 2-step TST is that the first test can stimulate the immune response, making the second test more accurate.

What Does a Positive TST Result Mean?

A positive TST result means you have been infected with TB bacteria, but it does not confirm active TB disease. If the TST result is positive, you may need a chest x-ray and a consultation with a doctor to rule out active TB disease. A negative TST result indicates that you are less likely to have TB.


Who Can Receive the TST?

Most people, including infants, children and pregnant women, can receive the TST. The only exceptions are those who have had severe reactions to a previous TST, such as skin necrosis or severe allergic reactions.

When Should You Avoid the TST?

If you have recently received live-attenuated vaccines (such as MMR, chickenpox, yellow fever, or nasal spray flu vaccine), you should avoid the TST because these vaccines can affect its accuracy.

What if You Need Both a Live-Attenuated Vaccine and the TST?

To ensure accurate TST results, you can either schedule the TST and live-attenuated vaccine on the same day or wait one month after receiving the live vaccine before taking the TST.

We hope this information helps those planning to study abroad. We welcome you to visit Shoebill Co-Traveller - Travel Health Management Center for your TST and other tests. Best wishes for your studies abroad!

Reference: Clinical Testing Guidance for Tuberculosis: Tuberculin Skin Test (CDC, 2024)