TB skin test please help!?

Question

I got a TB skin test a couple weeks ago and got it read after exactly 48 hours. The area was red, and there was a raised induration in my opinion. I could feel it raised as i ran my hand over the area. However, I got it read and they said it was negative. Could they have made a mistake? I am no doctor but judging by what I've seen and read, it seemed more positive to me.

Should I get another test done? I have always heard people say, never to get another skin test if you've had a positive test before. Why is that? What can happen if you get another skin test after you have tested positive in a skin test before? Will you get active TB? I am going into the medical field for my career and they do skin tests regularly once you are in the field. What should i do ?Please help me!

Answer 1

The raised area must be a certain size for it to count as positive. Normally if there is a raised, firm area, they will measure and record the size of the area, but if it is under the cutoff size it will be interpreted as negative. It is true that repeat tests are not recommended if you have had a positive test before, but in an unclear situation or if no records are available, the test may be repeated. The problem that can occur is the reaction can be much larger and cause more swelling, itching and discomfort. Repeated tests will NOT cause a positive reaction by themselves in someone not exposed to TB, nor will they cause latent TB to turn positive. I would address my concerns with the testing clinic if I were you. They may be able to explain the situation and reassure you why they read it as negative. It sounds like you are just now going into the medical field. If so, and if you have not had a TB test in over a year, I would agree with the two-step test (two tests placed a week apart). The reason for this is to make sure you are really negative as an exposure many years previously can result in a false-negative test that does not turn positive until the second test. This is called the "boosting" phenomenon. The problem that can arise in the case of someone who has only the one test is that later on, after working in the field, the person can have a positive test and it would be unclear if they were exposed on the job or earlier. Two-step tests are done only on initial employment or entry into the field; not annually.

People that test positive are followed up with a chest x-ray; if this is negative, they are treated for latent TB. Even if the person had BCG vaccine, a positive test is considered positive and treatment is recommended. BCG can cause a false positive, but it is impossible to tell this apart from a true positive skin test, especially when you consider that they came from a country with a high prevalence of TB and are at much greater risk of infection. Newer blood tests can be used in this case; they are not affected by BCG. A person who has tested positive in the past should not get additional skin tests. In that situation experts recommend annual screening for symptoms of active TB, with follow up testing as necessary. Annual chest x-rays for purposes of employment are NOT recommended.

Answer 2

I have not heard of any side effects from reactions to the TB test other than mild local reactions (swelling, redness) especially if you have a positive test. Usually it doesn't hurt much, it is a small needle and a small amount of liquid is injected intradermally (under the skin) it makes a small bubble. This bubble goes down and the skin will turn a little red, that's normal. You must wait 48-72 hrs to have the test read, you return to where you got it. Induration and swelling is a positive result (that you have been exposed to TB), a little redness is ok as long as the skin is not raised up like a welt or pimple, it's ok. When they read your test, the nurse will run her finger over your skin to make sure it's not raised at all. If it is, they will measure it, a positive result is either >5mm or >10mm of induration depending on risk factors and the physician, hospital or clinic's protocols. However, you have to wait the full 48 hrs to read the test, my arm will get a little swelling at first too but it goes away after the first day and by the time the test is read the result is negative (no exposure to TB)

Answer 3

Most of the time you should have 2 TB tests one week after each other so go get one. I really doubt you have TB, there is a little ball that is injected under your skin that leaves a little bump so that is probably what you noticed, it goes away. You should be fine.