Tuberculin Skin Test

A Tuberculin (Mantoux) Skin Test (TST) is performed to determine whether a person has been infected with the Tuberculosis (TB) bacteria. It tests for a latent TB infection, and not for an active TB disease. 

Not all those infected with TB show symptoms or become sick. Two TB-related conditions exist, namely TB disease and latent TB infection (LTBI). Those with LTBI show no symptoms, do not feel sick, and cannot infect others. Those with TB disease must seek proper treatment as, when left untreated, the disease can be fatal. 

TB is caused by the Mycobacterium tuberculosis bacterium. TB is most known to attack the lungs but can attack any part of the body, including the brain, kidneys, and lungs. Symptoms of TB largely depend on where the TB bacteria grow. TB in the lungs can include symptoms including a severe cough, lasting 3 weeks or longer, chest pain, as well as coughing up sputum (phlegm from deep inside the lungs) or blood. Other TB symptoms can include weight loss, lack of appetite, fever, chills, night sweats, weakness, or fatigue.  


A Tuberculin (Mantoux) Skin Test (TST), performed at Brintnell Pharmacy and Travel Clinic, is administered by injecting the inner surface of the forearm with a small amount (0.1ml) of tuberculin purified protein derivative (or PPD). The needle’s position during the injection is crucial. The bevel should face upward as an intradermal injection. When correctly placed, the injection results in a pale skin elevation (wheal) with a diameter of 6mm to 10mm. 

The result is read after 48 hours and not later than 72 hours after the injection has been administered by measuring the size of the firm swelling (induration) of the forearm if any. A negative test typically means that the person is not infected with the TB bacteria. A positive test typically means that the person has a latent TB infection. However, it can be the result of a TB vaccine (BCG) or a bacterial infection, like the Mycobacterium tuberculosis bacteria. 

If a person does not return within 72 hours of their test, they will need to be rescheduled for another skin test.  


At Brintnell Pharmacy and Travel Clinic, we provide Tuberculin Skin Test (TST) for health care students and employees. We have a pharmacist who has been trained to administer and interpret the TST.  

If you have a positive skin test result, you will be referred to a family doctor or Tuberculosis Services to have a chest x-ray done and possibly other tests.