October 18, 2013
How can we detect the microbe of tuberculosis?
The test consists of a tuberculin test commonly called TCT or tuberculin skin test. This is neither a cure nor a vaccine. This test helps determine if you have had recent or old contact with the germ of tuberculosis and whether you are at risk of developing the disease later.
TST requires two visits for you. At first, a small amount is injected with a substance called tuberculin into the skin at the front of the forearm. At the second visit, 48 to 72 hours after, an experienced person is reading the reaction.
If you already have a TST, it is important to mention, since you might not need it.
Fact Sheet on the tuberculin skin test (TST) PDF file.
What are the precautions to be taken after the TCT?
It is recommended that you apply anything on the site of the injection (eg adhesive tape, ointment) and does not irritate the injection site (eg scratching, wipe vigorously, soap).
You can continue your regular activities, take a bath or shower without problem. In case of itching, apply cold water compresses.
What are the possible reactions?
After 48 to 72 hours, redness and a small bump may appear at the injection site. Only an experienced person can measure the diameter of the bump.
It is very important to attend your appointment for reading test even if there is no redness or bump.
A negative reaction
A negative reaction means that you have never been in contact with the germ of tuberculosis or that your body has lost its ability to respond to the test.
If the tuberculin test is negative, it will be repeated in some people because the appearance of a positive reaction can sometimes take up to three months after the last contact to occur.
A positive reaction
A positive reaction means that the organization has met the tuberculosis microbe and has developed defense mechanisms that is latent TB infection. The vaccine against tuberculosis (BCG) can also cause a positive reaction.
It is possible that you recommend spending additional tests such as a chest x-ray and a medical examination to ensure that you are not suffering from pulmonary tuberculosis. The doctor may also recommend preventive treatment.
People who have been in contact with a case of tuberculosis are not contagious and pose no risk to their relatives.