TB test is not done necessarily after a patient has developed tuberculosis. The test is also done in order to see if the patient has latent, or silent, TB. The test is called the purified protein derivative test (PPD). The test is also known as the TB skin test, the Mantoux test or the Tuberculin skin test.
The test is administered in a doctor’s office or hospital. Upon arrival, the doctor will clean a part of your skin and he will give you an injection that contains the PPD. The needle is placed under the skin in a lateral manner allowing the PPD top form a welt or bump. This will subside as the hours go by.
The doctor will then ask you to go home and come back after 2 to 3 days. The doctor will then check the site to see if the result is positive. If you have an insurance carrier, you should tell them about the results of the PPD test, and they may ask you to take it again. If you are taking steroids, then you should let the doctor know since some drugs can lead to wrongful results.
The PPD test is very important since it tells if you have come into contact with the TB bacteria. TB can lay dormant in the lungs for years, a situation called latent TB. If you have been close to someone who has TB, then you need to take this test. If you also work in the provision of healthcare, you should also take the test.
If the results are negative, then this shows that you have never been affected by the TB virus. This is manifested by un-swollen skin, or one that has a very small swelling at the PPD site. Children, people with HIV and high risk groups use a different measure. The PPD test is not always true, and sometimes a negative has turned out to be false. The results may be negative in 1 out of every 5 people affected by the disease.
If the results are abnormal, then this may indicate that you have been infected with the TB bacteria. It is at this time that you should get treated when the bacteria is still latent. The results will also vary amongst individuals. Small reactions show infection in people with HIV, have had an organ transplant, with suppressed immunity or taking steroids, people who have come into close contact with someone who has TB.
Larger reactions show people who have never had the bacteria before, and have just been infected, people having diabetes, kidney failure and other conditions that encourage infection, healthcare workers, children under 4, people who inject drugs, people who have come from countries with high TB prevalence, people living in communities where the bacteria is multiplying, e.g., a school.
There is a small chance of getting severe swelling and redness in the skin, after you have had a positive PPD test and you want to have it again to confirm the results. Similarly, people who have never tested before may also develop this severe swelling. It is important that the doctor carry out further tests in order to determine whether you really have the disease, and also see if it is active or latent.
The vaccine BCG is also used to inoculate people, outside the United States of America, against this disease. If you have had a BCG injection then the test results will come back positive for TB. According to some experts, someone who has had a BCG shot in the past should not change the PPD result even when the test is done on people who are exposed to greater risk of getting this disease.