What to expect with the tuberculosis skin test
Tuberculosis is an airborne disease caused by an infection of the Mycobacterium tuberculosis bacteria. A TB skin test is the first method a doctor will use to try to determine if a person has TB.
This article explores what happens during a TB skin test, what the results might mean, and what to do once a person has them.
The skin test for TB, otherwise known as a Mantoux tuberculin test, can seem a bit intimidating, but it is quite straightforward.
The TB skin test has two parts. In the first, a doctor will inject someone with a small amount of a sterile solution, containing tuberculin.
Tuberculin is a fraction of purified protein derived from Mycobacterium tuberculosis. If an individual is infected with TB, their immune system will react to the tuberculin given in the TB skin test.
The injection is usually done on the inside of the forearm. When it is done correctly, the injection will create a small, pale-colored bump on the skin called a wheal.
The second stage of diagnosis must take place between 48-72 hours after the tuberculin injection.
At this appointment, the doctor will check to see what has happened to the wheal on the skin. If a person does not attend this appointment, they will have to start the process over again.
During the second appointment, a doctor will look to see how the body has responded to the injected tuberculin.
To do this, a doctor will measure the diameter of the wheal on the forearm and ask questions about the individual’s medical history and their environment.