Mantoux Test or Tuberculin Skin Test

The Mantoux test, also called the tuberculin skin test (TST) is commonly used for the diagnosis of tuberculosis (TB) in children. The Mantoux test or a tuberculin skin test (TST) is one of the methods of determining whether a person is infected with tuberculosis bacteria.

How is a Mantoux Test done?
Mantoux test involves injecting a small amount of a substance called Purified protein derivative (PPD) or tuberculin into the skin of the child’s forearm. This is done using a very fine 26G needle into the most superficial layer of the skin. The reaction to the test is read after 48-72 hours by a health care worker. The induration or the firm swelling is measured in millimetres across the child’s forearm. The erythema or redness is not considered.

What is Mantoux test positive?
A “positive” Mantoux test result is induration or firmness or bump more than 10 mm that occurs 48–72 h after the PPD is injected into the forearm of the child.

Does a Mantoux test confirm tuberculosis (TB)?
Children with a positive Mantoux test are infected with tuberculosis (TB) bacteria or mycobacterium tuberculosis. Most patients with a positive Mantoux test have a LATENT tuberculosis (TB) infection. Further tests are required to confirm whether the child has ACTIVE tuberculosis (TB). These include a detailed screening of the child's symptoms, good examination for presence of lymph nodes, a chest x-ray and ultrasound of the tummy.

Mantoux Test or Tuberculin Skin Test

Can a Mantoux Test be falsely positive?
Some children have a positive Mantoux test but are not infected with tuberculosis bacteria. The causes of these false-positive reactions could be prior vaccination with BCG vaccine, infection with nontuberculous mycobacteria (mycobacteria other than M. tuberculosis) and incorrect measurement or interpretation of Mantoux test.

Can a child with a negative Mantoux test have tuberculosis (TB)?
The Mantoux test is not a 100% sensitive test which means that a fraction of people with tuberculosis (TB) can have a negative test. False-negative reactions are related to factors like a recent TB infection (within the past 10 weeks), infants less than six months of age, recent vaccination with a live viral vaccine, incorrect method of administering and interpretation of TST reaction

What are the alternative tests available for diagnosis of Tuberculosis (TB)?
TB blood tests like Quantiferon TB test or also called interferon-gamma release assays or IGRAs are the alternate method of testing for tuberculosis (TB).

If your child has suspicion of tuberculosis (TB) or diagnosed with tuberculosis (TB) or has a positive Mantoux test you need to get in touch with a pediatric pulmonologist or tuberculosis specialist for proper diagnosis and treatment.

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