What does a positive Mantoux test indicate?

A positive Mantoux test indicates a possible tuberculosis infection due to the presence of an immune response to the tuberculin protein. This test involves the intradermal injection of purified protein derivative (PPD) and measuring the induration after 48-72 hours. When the immune system has previously been exposed to the bacteria that causes tuberculosis, it reacts to the PPD, resulting in a raised area at the injection site.

This response does not confirm an active infection but suggests that the person has been exposed to the bacteria, potentially indicating either a latent or active tuberculosis infection. Further diagnostic procedures, such as chest X-rays and sputum tests, are typically needed to confirm the presence of active tuberculosis.

The other options mention conditions unrelated to the Mantoux test; hence they do not represent the true interpretation of the results. The Mantoux test specifically assesses exposure to tuberculosis, not cancer, allergic reactions, or chronic lung conditions.