Introduction:
The Mantoux test, also known as the tuberculin skin test, is a diagnostic tool used to detect the presence of tuberculosis (TB) infection in individuals. This test involves injecting a small amount of purified protein derivative (PPD) into the skin of the forearm and observing the reaction. The Mantoux test is one of the most commonly used tests for diagnosing TB and has been in use for over a century. In this blog post, we will discuss the Mantoux test in detail, including how it works, its benefits, and potential risks.
The Mantoux tuberculin skin test (TST) is one method of determining whether a person is infected with Mycobacterium tuberculosis.
How does the Mantoux test work?
The Mantoux test works by detecting the presence of TB-specific proteins in the body. When the PPD is injected into the skin, it causes a local immune response, leading to the accumulation of white blood cells at the injection site. If an individual has been exposed to TB in the past, their immune system will recognize the PPD as a foreign substance and mount an immune response in the form of a raised, red bump at the injection site. The size of the bump is measured 48-72 hours after the injection to determine the result of the test.
Why is the Mantoux test performed?
The Mantoux test is performed to diagnose TB infection in individuals. TB is a bacterial infection that primarily affects the lungs but can also affect other parts of the body, such as the kidneys, bones, and brain. TB is a highly contagious disease and can spread through the air when an infected person coughs or sneezes. The Mantoux test is often used to screen individuals who are at high risk of contracting TB, such as healthcare workers, close contacts of TB patients, and individuals who have recently immigrated from countries with high TB prevalence rates.
How is the Mantoux test performed?
The Mantoux test is a simple and quick procedure that can be performed in a clinic or doctor’s office. The test involves injecting a small amount of PPD into the skin of the forearm using a needle. The injection site is then examined 48-72 hours later to determine the size of the raised, red bump that has formed. The size of the bump is measured using a ruler, and the result is recorded in millimeters.
Interpreting the results of the Mantoux test
The interpretation of the Mantoux test results depends on the size of the raised, red bump that forms at the injection site. A positive result is indicated when the size of the bump is 5mm or larger in individuals who are at high risk of contracting TB, such as HIV positive individuals, close contacts of TB patients, and individuals with weakened immune systems. A positive result may also be indicated in individuals who have recently immigrated from countries with high TB prevalence rates. However, the size of the bump indicating a positive result may be different in certain situations. For example, a positive result may be indicated if the size of the bump is 10mm or larger in individuals who are not considered to be at high risk of contracting TB.
What is a positive Mantoux test?
The test is “positive” if there is a bump of a certain size where the fluid was injected. This means you probably have TB germs in your body. Most people with a positive TB skin test have latent TB infection. To be sure, your doctor will examine you and give you a chest x-ray.
A patient who does not return within 72 hours will probably need to be rescheduled for another skin test. * For employees who are otherwise at low risk for TB and who are tested as part of an infection control screening program at the start of employment, a reaction of 15 mm is considered positive.
Potential Risks of the Mantoux Test
The Mantoux test is generally considered to be a safe and low-risk procedure. However, there is a small risk of developing a severe allergic reaction to the PPD. Other potential risks include pain, redness, or swelling at the injection site, and rarely, infection at the injection site. In some cases, the test may produce a false-positive or false-negative result, leading to further testing and unnecessary treatment or delayed diagnosis.
What is normal range of Mantoux test?
Your test results usually mention the diameter of the induration (localised swelling at the test site). The reference range of the induration is 0-15 millimetres at an increment of 5 mm, 10 mm and 15 mm. An induration size of more than 15 mm is considered positive in a normal patient.
How is a Mantoux test done?
The TB skin test is performed by injecting a small amount of fluid (called tuberculin) into the skin on the lower part of the arm. A person given the tuberculin skin test must return within 48 to 72 hours to have a trained health care worker look for a reaction on the arm.
How many mm is positive PPD?
Induration of 15 mm or more is considered positive in the following cases: Healthy individuals older than four years of age with a low likelihood of TB infection[14]
Is the Mantoux test confirmatory for TB?
A Mantoux test is an essential tool that aids in the diagnosis of TB. It is a useful diagnostic technique for identifying latent Mycobacterium tuberculosis infection. The test can also be used to detect an active infection. Sometimes your doctor may recommend additional tests to confirm the diagnosis.
Can the Mantoux test cause fever?
Yes, you might develop a fever as a side effect after taking the Mantoux test. However, the Mantoux skin test rarely causes any side effects. A person who has been exposed to TB germs, on the other hand, may occasionally have a significant reaction that causes moderate itching, swelling or discomfort. These kinds of responses should subside within one to two weeks.
Conclusion:
The Mantoux test is an important diagnostic tool used to detect the presence of TB infection in individuals. The test involves injecting a small amount of PPD into the skin of the forearm and observing the reaction. The results of the test can help healthcare professionals diagnose and treat TB infection early, preventing the spread of the disease to others. Although the Mantoux test is generally considered to be a safe and low-risk procedure, it is important to discuss any potential risks with your healthcare provider before undergoing the test.
