Tuberculosis : Tuberculin Skin Test (TST)

The Tuberculin Skin Test (TST), also known as the Mantoux test, is a widely used diagnostic tool for detecting Mycobacterium tuberculosis infection, the bacterium responsible for tuberculosis (TB). The test involves the intradermal injection of a small amount of purified protein derivative (PPD) into the skin of the forearm. After 48 to 72 hours, the injection site is examined for induration (a raised, hardened area), the size of which is measured in millimeters. The interpretation of the test depends on the size of the induration, with larger sizes generally indicating a higher likelihood of TB infection.

The TST is particularly useful for identifying latent TB infections, especially in high-risk populations. However, it cannot differentiate between latent and active TB, and its results may be influenced by factors such as previous Bacille Calmette-Guérin (BCG) vaccination and infection with non-tuberculous mycobacteria. Despite these limitations, the TST remains a key component in TB control strategies globally.