Induration >= 10mm
A hard, raised, palpable bump on the skin measuring 10 millimeters or more, indicating a positive cellular immune reaction to tuberculosis antigens.
Description
A clinician injects a small amount of tuberculin fluid intradermally into the inner forearm, creating a small wheal. Developed by Charles Mantoux in the early 1900s based on Koch's earlier work, the site is examined 48 to 72 hours later for induration. It determines if the patient has ever had an immunological exposure to the mycobacterium.