How does a positive TB skin test look?

A positive TB skin test, such as the Mantoux Test or tuberculin skin test (TST), is characterized by the presence of induration (raised, firm bump) at the test site. The appearance of the induration can vary depending on factors such as the individual's skin type, the volume of the purified protein derivative (PPD) injected, and the person's immune response. The induration is typically measured in millimeters (mm) within a specific time frame (usually 48 to 72 hours after the test administration) by healthcare professionals trained in TB management. The induration may have a palpable, firm texture, and its size is assessed using a ruler or calipers. The presence of a significant induration indicates exposure to the tuberculosis (TB) bacteria and the development of a delayed-type hypersensitivity response. The specific induration size that defines a positive result depends on various factors, including the person's risk factors, clinical presentation, and local guidelines. It is important to consult with healthcare professionals familiar with the current recommendations in your region to accurately interpret the test results and determine the appropriate next steps based on the individual's specific circumstances.