Why does TB skin test turn red?
Results. Redness alone at the skin test site usually means you haven’t been infected with TB bacteria. A firm red bump may mean you have been infected with TB bacteria at some time. The size of the firm bump (not the red area) is measured 2 to 3 days after the test to find out the result.
What happens after a positive TB skin test?
If you have a positive reaction to the TB blood test or TB skin test, your doctor or nurse will do other tests to see if you have TB disease. These tests usually include a chest x-ray. They may also include a test of the sputum you cough up.
What is the difference between erythema and induration?
The distribution of erythema diameters was unimodal, and the distribution of induration diameters was bimodal. Erythema was considerably greater than induration among persons classified as being atopic. Conclusion: Both erythema and induration appear to be adequate indices of tuberculin sensitivity.
What is borderline TB?
A borderline test result (T-Spot only) also indicates an uncertain likelihood of M. tuberculosis infection. A diagnosis of LTBI requires that TB disease be excluded by medical evaluation.
When do you read TB test results?
The TST is an intradermal injection of 0.1 ml of tuberculin (PPD) on the inner surface of the forearm. The skin test reaction should be read between 48 and 72 hours after administration.
What are the symptoms of a positive TB test?
A person with TB disease has a positive TB skin test , an abnormal chest x-ray (usually) and symptoms of TB disease (coughing for more than 3 weeks, fever, night sweats, fatigue, unexplained weight loss, loss of appetite, and/or others). A person with TB disease needs medication to become well.
What does a negative TB test look like?
As the provider examines your arm, then they can determine whether you have TB or not. In a negative response, the skin will most likely not be bright reddish, hard or look influenced. It will look like the day you received the injection , but there might be a little redness or indentation.
What are the types of TB tests?
There are two types of TB (tuberculosis) tests. One is a TB skin test (also known as a PPD test) and the other is a TB blood test (QuantiFERON ®-TB Gold).
What does false positive TB mean?
False negative test results can occur in many different medical tests, from tests for pregnancy , tuberculosis or Lyme disease to tests for the presence of drugs or alcohol in the body. Correspondingly, a false-positive test result indicates that a person has a specific disease or condition when the person actually does not have it.