What is a Mantoux test?
The Mantoux test, also known as the tuberculin skin test, is a diagnostic tool used to detect exposure to Mycobacterium tuberculosis, the bacteria that causes tuberculosis (TB). It is a widely used and highly sensitive test that can identify people who have been infected with TB, even if they don't have any symptoms.
What are the uses of the Mantoux test?
A Mantoux test is a valuable diagnostic tool used for identifying TB exposure in people with no disease symptoms. While the test is highly sensitive, false-positive and false-negative results can occur in some individuals, and further testing may be needed to confirm a diagnosis of active TB disease or LTBI.
What happens during a Mantoux test?
The Mantoux test involves injecting a small amount of purified protein derivative (PPD), a substance derived from the Mycobacterium tuberculosis, just under the surface of the skin on the inside of the forearm. The test is usually administered by a healthcare provider and takes only a few minutes to perform.
After the PPD is injected, the site of the injection is observed for a reaction over the next 48-72 hours. If a person has been exposed to the TB bacterium, their immune system will react to the PPD, resulting in redness, swelling, and hardening at the site of the injection. The size of the reaction is measured and interpreted by a healthcare provider.
A positive Mantoux test result indicates that a person has been exposed to the TB bacterium. However, it does not necessarily mean that the person has active TB disease. In fact, most people with a positive Mantoux test result do not have active TB disease and are not contagious. Instead, a positive result usually means that a person has been exposed to TB in the past and has developed an immune response to the bacteria.
People with a positive Mantoux test result may need further testing to determine whether they have active TB disease or latent TB infection (LTBI). LTBI is a condition where a person is infected with the TB bacterium, but does not have active TB disease. People with LTBI are not contagious and do not have symptoms of TB. However, if left untreated, LTBI can progress to active TB disease, which is a serious and potentially life-threatening condition.
Also, false-negative results can occur in people with weakened immune systems, such as HIV infection or certain types of cancer. These individuals may not mount a strong immune response to the PPD, leading to a negative Mantoux test result even if they have been exposed to TB.
Important information to know about a Mantoux test.
To minimize the risk of false-negative results, healthcare providers may use additional tests, such as chest x-rays or blood tests, to help diagnose TB in people who have symptoms of the disease or who are at high risk for TB infection.