Description
Sample Required:
Mantoux Tuberculin Skin Test: This test requires a small injection of tuberculin purified protein derivative (PPD) just under the top layer of the skin.
AFB Stain: For the Acid-Fast Bacilli (AFB) stain, a sample of sputum, urine, or other bodily fluids may be needed.
Test Time:
Mantoux Tuberculin Skin Test: The skin reaction is typically read 48 to 72 hours after the injection.
AFB Stain: Results are usually available within a few hours to a few days, depending on the laboratory’s processing time.
Test Normal Range:
Mantoux Tuberculin Skin Test: The test measures the size of the induration (raised, hardened area) at the injection site. Interpretation depends on risk factors and varies by region.
AFB Stain: Normal results for the AFB stain would show no acid-fast bacilli, indicating the absence of Mycobacterium tuberculosis.
What is the Test:
Mantoux Tuberculin Skin Test: This test checks for a delayed-type hypersensitivity reaction to proteins derived from Mycobacterium tuberculosis. It’s used to screen for tuberculosis (TB) infection.
AFB Stain: The Acid-Fast Bacilli (AFB) stain is a microscopic test that identifies acid-fast bacteria, such as Mycobacterium tuberculosis, in clinical specimens.
Test Procedure:
Mantoux Tuberculin Skin Test:
A small amount of PPD is injected under the skin, usually on the forearm. The injection site is checked 48 to 72 hours later for a raised, hardened area (induration). The size of the induration is measured and interpreted based on risk factors.
AFB Stain:
A sample of sputum, urine, or other relevant bodily fluids is collected. Special stains are applied to the sample, and it is examined under a microscope for the presence of acid-fast bacilli.
When to Take the Test:
Mantoux Tuberculin Skin Test: It may be recommended when there is suspicion of TB infection or as part of routine TB screening.
AFB Stain: This test is typically ordered when there are signs and symptoms of TB, such as persistent cough, fever, and weight loss.
Who Should Take This Test:
Mantoux Tuberculin Skin Test: Individuals at risk for TB, including healthcare workers, close contacts of TB patients, and those with specific risk factors.
AFB Stain: Individuals with symptoms suggestive of TB, as determined by a healthcare provider.
Precautions for Exceptional Cases (Pregnancy, etc.):
Pregnancy: The Mantoux Tuberculin Skin Test is generally considered safe during pregnancy. However, the decision to test pregnant individuals should be made in consultation with a healthcare provider, weighing the potential benefits and risks.
FAQs (Frequently Asked Questions):
Q1: What does a positive Mantoux Tuberculin Skin Test mean?
A: A positive result indicates exposure to TB or TB infection. Further evaluation, such as a chest X-ray and possibly treatment, may be needed.
Q2: Can the Mantoux Tuberculin Skin Test differentiate between latent TB infection and active TB disease?
A: No, it cannot. A positive result indicates exposure to TB or TB infection, but additional tests are needed to determine if the infection is latent or active.
Q3: How is TB treated if it’s confirmed by the AFB stain?
A: If TB is confirmed, a healthcare provider will prescribe a combination of antibiotics for several months to treat the infection.
Q4: Is it necessary to isolate someone with a positive AFB stain result?
A: Isolation measures may be necessary for individuals with confirmed active TB disease to prevent its spread. This decision is made by healthcare authorities.
Q5: Is the Mantoux Tuberculin Skin Test the same as the TB blood test (IGRA)?
A: No, they are different tests. The Mantoux test involves injecting a substance under the skin, while the TB blood test (Interferon-Gamma Release Assays or IGRA) measures the immune response to TB proteins in a blood sample.
