What Causes a False Positive TB Skin Test?
TB (an abbreviation for Tubercle bacillus) is caused by Mycobacterium tuberculosis; a slow growing, wax-coated acid-fast bacterium that can remain viable in dried aerosol droplets for eight months. Although not considered highly infectious, it takes few M. tuberculosis bacteria to start a disease process that can destroy lung tissue, disseminate and result in death. The Mantoux Tuburculin Skin Test Those in the medical field, and others with a high risk of contracting tuberculosis, are routinely tested with the Mantoux tuberculin skin test (TST). The TST involves injection of a minute amount of tuberculin purified protein derivative (PPD) into the inner surface of the forearm. How the TST Works The immune system of those infected with the Mycobacterium tuburculosis will react to the PPD protein, which is an antigen derived from the bacteria’s cell wall. For those with TB, the TST mimics reexposure to the pathogen, and reveals the rapid immune response of antibodies that would be presen
