Test Name: Tuberculin test
Normal Range: Negative 0-5 suspicious 5-10 positive>10
To help determine whether or not you may have been exposed to and become infected by the Mycobacterium tuberculosis () bacteria
- When you have diseases or conditions that weaken your immune system and put you at a greater risk of developing active tuberculosis.
- When you have had close contact with someone who has active TB, or work or live in a high risk environment.
- When you have lived for a period of time in a foreign country where TB may be more common.
- Sometimes as part of an examination prior to starting a new job (such as a healthcare worker).
No sample is required. A small amount of purified protein derivative (PPD) solution is injected just under the first layer of skin of your inner forearm.
is an infectious disease caused by a bacterium named Mycobacterium tuberculosis. It may affect many body organs, but primarily affects the lungs (pulmonary). Tuberculosis, (once called consumption), has been a common cause of death for thousands of years.
TB may cause a latent or inactive infection or an active, progressive disease. About 90% of the people who become infected with TB manage to control its growth and confine the TB to a few cells in the body. The bacteria in these cells are inactive but still alive. The patient is not sick, they do not have any symptoms, and they are not infectious, but they do have a "latent TB infection." If the patient's immune status is later compromised, the latent TB bacteria may begin to grow again, leading to an active case of tuberculosis disease. This active TB does cause illness in the patient and it can be passed to others through respiratory secretions such as sputum (spit or phlegm) or aerosols released by coughing, sneezing, laughing, or breathing.
If the test is positive, further testing will be done to look for signs of active tuberculosis. This could involve an X-ray.
How is the sample collected for testing?
No sample is required. The test is performed on the patient's skin. A purified protein derivative (PPD) solution that contains TB antigens, but not live bacteria, is used to provoke a hypersensitivity skin reaction (a red raised bump) in those who may have been infected by TB.
A healthcare professional will wipe your inner forearm with alcohol and let the skin dry. Using a syringe and a tiny needle, they will inject a small amount (0.1mL) of PPD solution just under the first layer of your skin. When done correctly, the injection forms a small bubble of fluid that looks like a blister. The site should be left uncovered and undisturbed; and perfumes and other cosmetics should not be applied. It will then need to be examined by a healthcare professional at 48 and/or 72 hours after the injection to see if a local skin reaction has occurred.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.