Mantoux Test
Mantoux Test
The Mantoux test, also known as the tuberculin sensitivity test (TST), is a skin test helpful in determining if a person has ever been exposed to tuberculosis bacteria (Mycobacterium tuberculosis) or if they require treatment. The test involves injecting a small amount of testing fluid (called tuberculin) derived from dead TB bacteria under the surface of the skin on the forearm to measure the size of the immune reaction occurring in response three days later.
Tuberculosis is a contagious disease of the lungs and respiratory system, but it can also affect the brain, kidneys, and spine. The disease spreads through coughing, sneezing, and from organ donations by infected individuals. However, not all infected individuals exhibit symptoms, but they may develop latent TB infection. Without treatment, these individuals are at high risk of developing active TB disease, which may turn deadly.
What is the Mantoux Test Used For?
Mantoux test is done
To find people with latent TB infection who may have been exposed to someone diagnosed with an active TB disease
To check if people have latent TB infection before they start working at a healthcare facility or travel to places with a high TB burden
Before administering BCG (bacille Calmette-Guérin) vaccine
Symptoms of Tuberculosis
People infected with latent tuberculosis do not develop symptoms but, on eventual reactivation of TB infection, can experience
Bad cough that lasts 3 weeks or longer
Coughing up blood and mucus
Extreme tiredness
Fever and chills
Sweating at night
Unexpected weight loss
Chest pain
Loss of appetite
Preparation for Test
There is no food or water restriction before or after the Mantoux test. But inform your doctor if you:
- have ever been treated for TB
- had a Mantoux test
- had a viral illness that weakened your immune system
- took any medication, such as steroids
- received any vaccinations in the past month
Interpretation of Test Results
The results of the Mantoux test are interpreted by examining the size of the raised, hard area or swelling (in millimetres) that appears three days after the test and may look different for everyone, depending on risk factors.
|
Size of the swelling |
Result |
|
Less than 5 mm |
Negative (not likely to be infected with TB bacteria), although repeat testing after 8-12 weeks is needed to rule out
|
|
At least 5mm or more |
Positive if you: Have weak immunity |
|
≥ 10mm |
Positive if you:
|
|
≥ 15mm |
Positive for people with no known risk factors for TB |
FAQs
Is the Mantoux test painful?
There is a slight risk that you may have a severe allergic reaction to the testing fluid if you have had TB. You may experience a lot of swelling or pain at the injection site.
What precautions should I take after the Mantoux test?
After the test, make sure to avoid bandaging or scratching the area where the testing fluid is injected because it can affect the results.
What does a positive Mantoux test result mean?
A positive Mantoux result indicates that you have been exposed to TB bacteria and may have a latent form of TB. At this stage, you may not have symptoms and, therefore, may not be at risk for spreading the bacteria, but you may develop the disease in the future. So, your doctor may order additional diagnostic tests to confirm TB.
Is the Mantoux test confirmatory for TB diagnosis?
No, the Mantoux test isn’t confirmatory to diagnose TB. It just tells you if you have been infected with TB bacteria. But it can’t tell if a person has a latent infection or an active TB disease.
Must everyone take the Mantoux test?
The Mantoux test is generally not suggested for people with a low risk of tuberculosis infection. However, people with HIV infection, babies and young children, older adults, people with weakened immunity, and those who have previously not been fully treated for tuberculosis must take this test since they are more likely to develop the TB disease.
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