Positive evidence of tuberculin hypersensitivity will be detected within 48 to 72 hours by local swelling and redness of the area followed by necrosis and fever. Reactivity to tuberculin indicates that the person had been previously infected with tubercle bacilli. This test, however, does not differentiate between active and inactive tuberculosis infection. For more information, go to Columbia University's TB Web site . However, a positive tuberculin test does not differentiate between active and inactive tuberculin infection.
Active tuberculosis results due to the release of bacilli that survive within the granulomas.
Some theories have been proposed as to the reason for the persistence of these bacilli within the granuloma. It has been noted that mycobacterium can remain dormant under anaerobic conditions inside the granuloma. Also, others have proposed the existence of microspores or cell wall free bacilli. However, still others believe that bacilli are not in fact dormant, but replicating at a very slow rate. This rate can be matched by the host immune system, thus destroying the bacilli at a comparable rate.