Redness Vs. Induration: the Critical Tb Skin Test Mistake Most People Make
A confirmed positive Mantoux result does not mean you have an active, transmissible infection. In fact, roughly 90% of individuals who test positive carry latent tuberculosis infection. In latent cases, your immune system successfully isolates the bacteria inside tiny cellular capsules called granulomas. The bacteria stay alive, but they remain dormant. You have no symptoms, feel entirely healthy, and cannot transmit the pathogen to anyone else.
By contrast, active TB disease occurs when the bacteria overcome your immune defenses and multiply unchecked, causing persistent cough, hemoptysis (coughing up blood), unexplained weight loss, night sweats, and persistent fevers. Active disease is airborne and highly contagious.
The skin test cannot differentiate between these two states. It functions solely as an indicator of biological exposure. If your induration meets the positive millimeter threshold, clinicians immediately order a chest X-ray confirmation and conduct a structured symptom review. Clear lung imaging paired with an absence of respiratory symptoms confirms a latent state, opening the door for preventive antimicrobial therapies like rifampin or isoniazid regimens that eliminate the dormant bacteria before they ever reactivate.
