Admin_NHT Staff asked 6 years ago Tuberculosis skin testing, also known as Mantoux Tuberculin Skin Testing (TST), is used to determine if a person is infected with Mycobacterium Tuberculosis. TST is administered as an intradermal injection given on the forearm where about 0.1ml of tuberculin purified protein derivative is injected. A skin test reaction is usually available 48-72 hours after administration and it is rescheduled if the patient fails to show up after 72 hours.
After 72 hours, the reacted area (palpable, raised, hardened, or swelling) is measured in millimetres and depending on the size, the risk of infection is evaluated. Area of 5mm or more is usually considered positive. The test might also give certain false-positive reactions if the person is infected with non-tuberculosis mycobacterium or if he has received BCG vaccination. TST is normally not performed on infants, children, pregnant women, BCG vaccinated individuals, or HIV-infected individuals.