What qualifies as a positive Mantoux test result?

A positive Mantoux test result is defined by the amount of induration, which is a localized area of swelling that hardens at the injection site, typically measured 48-72 hours after administration.

The criteria for a positive test can vary based on a person’s risk factors and medical history. For most individuals, an induration of more than 10 mm is considered significant and indicates a likely infection with Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). This threshold is especially relevant in the context of individuals who do not have compromised immune systems or specific risk factors.

In populations at higher risk, such as those with close contacts to tuberculosis patients, HIV-positive individuals, or people with certain pre-existing health conditions, a smaller induration (5 mm or more) may also be classified as positive. For most healthy individuals, however, the standard threshold is set at more than 10 mm to minimize false positives and accurately identify those who may benefit from further evaluation and treatment.

This understanding is critical for effective screening and intervention in public health, especially in areas where tuberculosis is more prevalent.