Introduction
The Mantoux tuberculin test is a skin test to check if a person has been infected with TB bacteria.
The Mantoux test or Mendel–Mantoux test also known as the Mantoux screening test, tuberculin sensitivity test, Pirquet test, or PPD test for purified protein derivative, is a tool for screening for tuberculosis (TB) and for tuberculosis diagnosis.
The Mantoux tuberculin skin test (TST) is one method of determining whether a person is infected with Mycobacterium tuberculosis. Reliable administration and reading of the TST requires standardization of procedures, training, supervision, and practice.
A TB skin test requires two visits with a health care provider. On the first visit the test is placed; on the second visit the health care provider reads the test.
A skin test is the only way to tell if you have TB infection. The test is "positive" if a bump about the size of a pencil eraser or bigger appears on your arm. This bump means you probably have TB infection.
The reaction is read by measuring the diameter of induration (palpable raised, hardened area) across the forearm (perpendicular to the long axis) in millimeters. If there is no induration, the result should be recorded as "0 mm". Erythema (redness) should not be measured.
The reference range of the induration at the site of injection of tuberculin is 0-15 mm at an increment of 5 mm, 10 mm and 15 mm. An induration size of more than 15 mm is always considered positive in a normal patient. A swelling of less than 4 mm is considered negative Healthy individuals without any risk factors for TB shows negative test.
Negative TST means the person's body did not react to the test, and that latent TB infection or TB disease is not likely.
Using a small needle, a health care provider injects a liquid called" tuberculin" into the skin of the lower part of the arm. When injected, a small, pale bump will appear.
Mantoux test can be repeated:
The test may be seen as positive if the skin where you were injected is hard, raised, red, and swollen. But "redness alone is not considered a positive test result." In many cases, a healthy immune system will surround the TB bacteria soon after you are infected.
Negative result means that you have not been infected with TB bacteria. However, if your contact with TB was very recent, you may need to have the test repeated in 8 to 12 weeks. A false negative can occur if you are unwell, have a weak immune system, or have had a recent live vaccination.
The PPD skin test is a method used to diagnose silent (latent) tuberculosis (TB) infection. PPD stands for purified protein derivative.
Purified protein derivative test (PPD skin test), administered through the Mantoux technique, is a type IV hypersensitivity skin reaction to 'tuberculin. ' Therefore, also known as the tuberculin skin test (TST skin test).
The TST is performed by injecting 0.1 ml of tuberculin purified protein derivative (PPD) into the inner surface of the forearm. The injection should be made with a tuberculin syringe, with the needle bevel facing upward. The TST is an intradermal injection.
Mantoux test can be false positive and false negative.
Immunization with the BCG vaccine is also known to give false positive results in the Mantoux test. The Mantoux test may also yield false negative results in immunocompromised patients due to the incompetency of the immune system to generate an adequate reaction to PPD.
False-positive reaction: A positive skin test reaction in a person not infected with M. tuberculosis.
Nontuberculous mycobacteria (NTM): Mycobacteria other than those comprising the M. tuberculosis complex. NTM may cause pulmonary disease resembling TB; however, NTM are not usually spread from person to person.
Information compiled by: Dr Bhairavsinh Raol
