Tuberculin

Tuberculin is an extract from the tubercle bacillus, a bacterium that causes tuberculosis. It is used to diagnose tuberculosis (TB) infection, or to test for a person’s immunity to the disease. It is injected just underneath the skin, and the results of the test are determined by the body’s reaction to the injection. If a person has been exposed to TB, the body will produce a reaction to the tuberculin, which can be detected by a health professional. The test is also known as the Mantoux test.

Tuberculin, also known as tuberculin purified protein derivative (PPD), isn't a medication itself, but a diagnostic tool used to detect tuberculosis (TB) infection. Here's a breakdown of its role:

Function:

• TB Test: Tuberculin is used in a skin test known as the Mantoux test or PPD test. This test helps determine if someone has been exposed to the bacteria that causes TB, Mycobacterium tuberculosis.
• Immune Response: When someone is injected with a small amount of tuberculin intradermally (into the skin), the body's immune system reacts if it has encountered TB bacteria before.
• Positive Test: If a person has been infected with TB in the past, even if they don't have active TB disease, their immune system will trigger an inflammatory response at the injection site. This results in a raised, hardened area within 48-72 hours. The size of the induration (hardening) determines the test result.

Things to Know About Tuberculin:

• Doesn't Cause TB: The tuberculin test doesn't cause TB infection. It only detects a past exposure.
• Limitations: The tuberculin skin test isn't perfect. It can sometimes produce false positive or negative results. Other factors like BCG vaccination (for TB prevention) can also influence the test result.
• Who Gets Tested: Doctors may recommend a tuberculin skin test for people at high risk of TB infection, such as healthcare workers, people from regions with high TB rates, or those with weakened immune systems.