Mantoux test

The Mantoux test is a widely utilized diagnostic tool for detecting infection by Mycobacterium tuberculosis, the bacterium responsible for tuberculosis (TB). It measures the body's immune response to a derivative of the bacterium, rather than the bacterium itself.

Mantoux tuberculin skin test

Negative Mantoux Test

Mantoux Test 48h

Procedure

The test is administered by injecting a small amount of tuberculin purified protein derivative (PPD) into the dermis layer of the skin, usually on the inner forearm. The injection site is observed after 48-72 hours to determine the body's reaction to the tuberculin.

Interpretation

The key feature of the Mantoux test is the size of the induration (a hard, raised area), not the redness, at the injection site after 48-72 hours. The diameter of the induration is measured in millimeters. The interpretation of the test depends on the size of the induration and the patient's risk factors for tuberculosis.

Limitations and False Results

The test does not differentiate between latent tuberculosis infection (LTBI) and active tuberculosis disease. It also does not distinguish between infection acquired recently and that acquired in the past. False-negative results may occur in individuals with impaired immune systems, while false-positive results can occur in those vaccinated with the BCG vaccine or infected with non-tuberculous mycobacteria.

Follow-up Testing

A positive Mantoux test indicates exposure to M. tuberculosis and warrants further investigation, such as a chest X-ray or sputum culture, to differentiate between latent infection and active disease.

See Also

• Tuberculosis
• Latent tuberculosis
• BCG vaccine