The tuberculosis skin test is a skin test which could be used for the detection of immune response to the bacterium(TB).
This immune response can happen when someone currently has active TB infection, or they were exposed to TB infection in the past, or if they received the had been vacinated TB (such as in China and other asian countries). The WHO estimates that 2 billion people worldwide have latent TB infection, while around 3 million people worldwide die of TB per year.
This immune response can happen when someone currently has active TB infection, or they were exposed to TB infection in the past, or if they received the had been vacinated TB (such as in China and other asian countries). The WHO estimates that 2 billion people worldwide have latent TB infection, while around 3 million people worldwide die of TB per year.
The tuberculosis skin test is also known as the tuberculin test or PPD
test. PPD is the abbreviation of purified protein derivative. The mechanism of the PPD test is in fact with the infectionof M. tuberculosis
bacterium. The bacterium produces a delayed hypersensitivity skin reaction ( like athma is also a delayed hypersensitive reaction).The components of the organism are added into the extracts of culture filtrates and as the core elements of
the tuberculin PPD.
Reaction in
the skin to tuberculin PPD begins with T cells which have been sensitized by prior infection. These sensitized T cells are recruited by the
immune system to the skin site, and then release chemical messengers lymphokines. These lymphokines induce induration through local vasodilation leading to fluid deposition known as edema, fibrin deposition, and recruitment of other types of inflammatory cells to the area.
The incubation period of TB are usually 2 to 12 weeks which is necessary for the PPD test to be positive.
Anyone can have a TB test, licluding infants, pregnant
women, or HIV-infected people with no danger. It is only dangerous
in people who have had a severe reaction to a previous tuberculin skin
test.
To perform the PPD test, you will need to see your doctor twice. At the first visit, the health care provider will clean an area of your skin and injecte a small amount of PPD. The needle is gently placed under the top layer of skin, causing a bump (welt) to form which usually goes away in a few hours.
The most important visit is the second visit which is after 48-72 hours of the shot, you must return to your doctor's office to check the area to see if you have had a significant reaction to the PPD test.
And this is done for our international student every year:)
To perform the PPD test, you will need to see your doctor twice. At the first visit, the health care provider will clean an area of your skin and injecte a small amount of PPD. The needle is gently placed under the top layer of skin, causing a bump (welt) to form which usually goes away in a few hours.
The most important visit is the second visit which is after 48-72 hours of the shot, you must return to your doctor's office to check the area to see if you have had a significant reaction to the PPD test.
And this is done for our international student every year:)
This post reminds me that I need to get my TB skin test for next year. The other day, I heard a story on the radio of a Subway worker who was diagnosed with Tuberculosis. I can't remember exactly where it was, but I feel like it may have been Tuscaloosa for some reason. Wherever it was, the worker was diagnosed. They tested the rest of the workers, but all came back negative. I know this put a scare in the people of the area. Everyone doesn't know that tuberculosis can't be spread through the handling of food, so I'm sure the citizens of the ares went to get tested as well.
ReplyDeleteWhen visiting the UAB micro lab, they have a special, negative pressure room just for TB testing; not the ususal skin TB test, but actual diagnosis of infection with the organism. I had never been in a negative pressure room, but it does not allow air to leave the room, but air can come in. This is so that in the case a TB organism is in the air, it cannot leave the room and will be confined in there so that it won't affect anyone else in the hospital. In the tour they mentioned that they have about twenty cases of TB a year, which was shocking to me. I thought the numbers would be much smaller here in the US.