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Tuberculin skin test – Outdated or still useful for Latent TB infection screening?

Whilst the tuberculin skin test (TST) (better known as the Mantoux Test to older-generation physicians) is over a century old, it continues to be used in high endemic TB settings as a diagnostic tool for determining latent Mycobacterium tuberculosis (MTB) infection (LTBI). The TST measures delayed type hypersensitivity (DTH) response to intradermal injection of purified protein derivative (PPD), a crude mixture of several mycobacterial antigens which are common to M. tuberculosis, Mycobacterium bovis BCG, and non-tuberculous mycobacteria (NTM). Thus, a positive TST test is of low specificity and cannot differentiate between M. tuberculosis infection, prior BCG vaccination, infection with or…

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Articles of Interest

Administering, reading and interpreting a tuberculin skin test

The standard method of identifying people infected with M. tuberculosis is the TST using the Mantoux method. Multiple puncture tests should not be used as these tests are unreliable (because the amount of tuberculin injected intradermally cannot be precisely controlled).

I’ve got TB - but how?

'It seems to be positive," said the doctor, examining the red swelling on my forearm. Three days earlier, a nurse had told me to look away before she injected fluid into that spot. She was performing a skin test for tuberculosis (TB). I had volunteered for a research programme at Manhattan's Bellevue hospital, and the test was required. My nurse was so confident of a negative result that she had taken a ballpoint pen and drawn a circle around the area on my arm in case she couldn't locate it later... To my horror, the pen circle became a red mound, then a large scarlet antagonist. It sniggered at me in the shower, itched, and glared reproachfully. No, I thought, this can't be.

My TB skin test came back positive… Now what?

After receiving positive results the first step is for the individual to get a chest x-ray to make sure there is not an active infection going on in the lungs. If the chest x-ray is clear and they are not having any symptoms, chances are the person has a latent TB infection. Latent TB means they have been exposed to someone with active TB and have the bacteria in their body, but it is not growing. Latent TB can not be spread to anyone. Anyone with a positive skin test has the option of being treated for latent TB to reduce the risk of developing active TB. Treatment is usually 9 months long. It is estimated that once exposed and develop latent TB you have about a 10% life time risk of developing active TB (given that you have a healthy immune system). The risk is much higher for anyone with a low immune system.

New TB skin test could offer cheaper and easier way to detect the disease

We developed a patch, similar to a plaster (adhesive bandage), that could detect some of the chemicals from the TB bacteria. We found we were able to distinguish between TB-positive and TB-negative individuals. Our research holds promise for an inexpensive test that could be easy to transport and simple enough so that it would not need a healthcare worker to administer.

Skin Test Of TB | Skin Test Positive And Allergic Reaction

While widely used, the TST has limitations, such as cross-reactivity with BCG and the potential for false positives due to non-TB mycobacterial exposure. Despite these challenges, the TST remains a valuable tool in skin test of tb diagnosis, complementing other methods and contributing to global skin test of tb control efforts.

TB (tuberculosis) skin test

The result is known two to three days later when the skin is examined. If the test is positive, your doctor will ask if you have had a positive TB skin test in the past and if you have any symptoms that might indicate active TB. Your doctor will likely order a chest x-ray, even if you feel fine.

TB Skin Test

Tuberculosis, or TB, is a highly contagious, infectious disease of the lungs that causes chronic coughing, weight loss, fever and death. Fortunately, a TB skin test is about as simple as it gets for diagnosing the infection: Doctors prick the skin, inject a small amount of TB proteins, and two to three days later check for a raised bump indicating an immune response.

Tuberculin skin test interpretations

All nurses learn how to administer and interpret TB skin tests and that a result of ≥10 mm induration is positive. The test can be given as a one- or two-step screening. In the one-step protocol, the nurse administers the PPD vaccine intradermally to the patients’ forearm and interprets the result within 48 to 72 hours. If the results aren’t read within that timeframe, the result becomes invalid and the test must be repeated. In the two-step protocol, a negative result after 48 to 72 hours requires a repeat test within 1 to 4 weeks.

What You Need to Know About the TB Skin Test

Getting tested and treated for tuberculosis (TB) can protect yourself, your family and friends, and your community. There are two types of tests for TB infection: the TB blood test and the TB skin test. This fact sheet provides information on the TB skin test

Why Finding A TB Test Got Hard

If PPD tests can't be found, the CDC recommends an IGRA blood test. It's a bit more invasive because it requires a blood draw, but can be more accurate, particularly in people who have had a BCD TB test, which is used in other countries.

Resources

PPD Skin Test

Robert Koch described the tuberculin reaction in 1890, and Felix Mandel developed the test in 1908. Charles Mantoux was credited with creating the technique of injecting material intradermally on the inner surface of the forearm. In 1934, Florence Seibert published her method of obtaining the purified-protein derivative, effectively creating the PPD test.

TB Skin Testing

TB skin testing is also known as a PPD or a Mantoux test. PPD stands for purified protein derivative. A health care professional injects a small amount of fluid under the skin of the forearm. We check the area for a reaction in 48-72 hours.

CDC

The skin test reaction should be read between 48 and 72 hours after administration by a health care worker trained to read TST results. A patient who does not return within 72 hours will need to be rescheduled for another skin test.