Tuberculin test

Tuberculin test is a medical test used to diagnose tuberculosis, an infectious disease caused by the bacterium Mycobacterium tuberculosis. The test is also known as the Mantoux test, PPD test, or Tuberculin Skin Test (TST).

Overview

The tuberculin test involves injecting a small amount of tuberculin into the skin. Tuberculin is a protein derivative (PPD) of the tuberculosis bacterium. The body's immune response to this injection is then measured to determine whether the person has been exposed to tuberculosis.

Procedure

The test is usually performed on the forearm. A small amount of tuberculin is injected under the skin, creating a small raised bump. The test is read 48 to 72 hours later by a healthcare professional who measures the size of the induration (swelling) in millimeters. The interpretation of the test depends on the person's risk factors for tuberculosis and the size of the induration.

Interpretation

The interpretation of the tuberculin test can be complex, as it depends on various factors including the person's risk of being infected with tuberculosis, the likelihood of progression to disease if infected, and the potential benefits of tuberculosis treatment. A larger induration is more likely to indicate a true positive result, but smaller indurations may also be significant in certain populations.

Limitations

The tuberculin test has several limitations. It cannot distinguish between latent tuberculosis infection and active tuberculosis disease. It also cannot differentiate between infection with Mycobacterium tuberculosis and vaccination with BCG vaccine. False positive and false negative results are also possible.

See also

• Tuberculosis
• Mycobacterium tuberculosis
• BCG vaccine
• Tuberculosis treatment

References

Tuberculin test Resources
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