PPD Tuberculin Skin Test or Mantoux Test

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What Is PPD Tuberculin Skin Test or  Mantoux Test 

Mantoux Mandel skin test also known as PPD test and Tuberculin Sensitivity Test, is the standard method that can show if you have presence of TB infection. The Mantoux tuberculin skin test does not differentiate between active and latent TB. It only tells presence of tuberculosis bacteria. If this test is positive doctor may advice another test to confirm the active TB infection.

Read here: Difference Between Latent TB vs Active TB

Method For Mantoux Test or PPD Skin Test

A standard dose of PPD (Purified protein derivative) tuberculin is injected intradermally in the skin (between the layers of dermis) This intradermal injection is termed the Mantoux technique. A person who has been exposed to the bacteria is expected to mount an immune response in the skin. The skin is read 48 to 72 hours later after administration of injection.

Interpretation for PPD Tuberculin Skin Test

The interpretation is based on the sensitivity of skin to injected PPD tuberculin. The reaction is read by measuring the diameter of palpable – raised hardened- area ( induration) area across the forearm. The reader should not measure erythema (redness). The appearance of induration does not mean that you have TB. Because different diameters of induration are considered positive in different kind of individuals.

For example. An induration of 5 or more millimeters is considered positive in HIV-infected persons. Induration of more than 10mm is considered positive for children under 4 years of age. so you should depend on your doctor or expert for interpretation.

False Positives to PPD tuberculin test:

Some persons may react to the tuberculin skin test even though they are not infected with tuberculosis. The causes of these false-positive reactions may include, but are not limited to, the following:

• Infection with non-tuberculosis Mycobacteria
• Previous BCG vaccination
• Incorrect method of TST administration
• Incorrect interpretation of reaction
• Incorrect bottle of antigen used

False Negatives to PPD tuberculin test :

The reasons for these false-negative reactions may include, but are not limited to, the following:

• Cutaneous anergy (anergy is the inability to react to skin tests
• because of a weakened immune system)
• Recent TB infection (within 8-10 weeks of exposure)
• Very old TB infection (many years)
• Very young age (less than 6 months old)
• Recent live-virus vaccination (e.g., measles and smallpox)
• Overwhelming TB disease
• Some viral illnesses (e.g., measles and chicken pox)
• Incorrect method of TST administration
• Incorrect interpretation of reaction

Side Effects of PPD Skin Test?

Mantoux test does not have any side effects in most individuals. There is very slight risk of reaction like swelling and redness of the arm, this can be controlled by doctor if happens. Allergic reactions are also rare complications.

There is no chance of developing tuberculosis from the PPD test.

What If You Got Positive Skin Test?

If your PPD tuberculin test is positive, do not panic. because

• Active Tb is still not confirmed.
• Latent Tb can be cured easily by taking one medicine for some months.
• If other Tests confirm active TB then it can always be cured in few months.
• Tb diagnosis and treatments are free in India by government, and also easily accessible.

Who Should Have A TB Skin Test

• Those who have had frequent close contact with someone who has active TB disease
• Those living or lived in a country or locality where many people have TB
• Those working or living in a nursing home, clinic, hospital, prison, or homeless shelter, or
• Those who have HIV infection or certain other health problems.
• Consult your doctor about possibility if you have cough for more than 4 weeks.

Please note, doctor may suggest other tests directly like chest X-ray and sputum test without first suggesting Mantoux test. Mantoux tells about presence of tuberculosis bacteria in latent state or active state. Other tests may confirm the active Mycobacterium TB infection.

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