Diagnostics
Tuberculin Test
What is tuberculin test?
The Tuberculin skin test, also known as the Mantoux test, is a diagnostic tool used to determine if a person has been exposed to tuberculosis (TB) bacteria.
Who performs the tuberculin test?
A nurse, doctor, or trained laboratory technician will administer the tuberculin test by injecting the medicine into the skin of the forearm in a hospital or clinic setting.
How the tuberculin test is performed?
Test Administration
The tuberculin test consists of two parts:
Part one: A nurse, doctor, or trained laboratory technician will inject a small amount of tuberculin under the skin, usually in the forearm. Tuberculin is a substance made from the bacteria that cause TB. After the injection, a small, pale bump will form at the injection site.
Part two: After 48 to 72 hours, a doctor examines the area where the injection was administered to measure the size of the induration (swelling or bump) that has occurred. The size of the induration is used to determine whether the patient has been exposed to TB bacteria.
Interpreting the Results
The doctor will check the test site for reactions within 48 to 72 hours after the injection. A raised, red bump at the site of the injection indicates a positive reaction. A doctor will measure the induration (raised bump) across the forearm, perpendicular to the axis between the hand and elbow. A negative reaction means there is no significant bump or only a small bump at the injection site.
Positive Result
A positive tuberculin test does not necessarily mean that the patient is suffering from active tuberculosis disease. It indicates exposure to TB bacteria at some point in life. Further evaluation, such as a chest X-ray or sputum culture, may be required to determine if the infection is active or dormant. Additional testing helps differentiate between latent TB infection (LTBI) and active TB disease.
Side Effects
The tuberculin test is generally safe but can cause a small bump and redness at the injection site. Rarely some individuals may experience an allergic reaction.
It is important to inform the doctor about any known allergies or previous adverse reactions to the tuberculin test.
References
- Centers for Disease Control and Prevention (CDC). (2021). Tuberculin Skin Testing Fact Sheet. Available from: https://www.cdc.gov/tb/publications/factsheets/testing/skintesting.htm
- Tuberculin (Intradermal Route). Available from: https://www.mayoclinic.org/drugs-supplements/tuberculin-intradermal-route/description/drg-20066571
- Tuberculin (Intradermal Route). Side effects. Available from: https://www.mayoclinic.org/drugs-supplements/tuberculin-intradermal-route/side-effects/drg-20066571
- How to identify a positive Tuberculosis (TB) Skin test: Available from: https://www.healthline.com/health/what-does-a-positive-tb-test-look-like#identifying-infection
