Mantoux Test
The Mantoux test is performed to determine whether a person has ever been exposed to tuberculosis. However, this skin test cannot determine if the infection is active or in a latent state.
General Description
The Mantoux test, or tuberculin test, is a skin test used to check if a person’s body is infected with tuberculosis. This procedure detects the body’s sensitivity to the proteins of the Mycobacterium tuberculosis bacteria (Koch’s bacillus). When the result is positive, it indicates that the person has been exposed to the infection at some point, but it does not provide information on when. In other words, it cannot determine whether the disease is active (which can be contagious) or latent.
When is it indicated?
The tuberculin test is indicated in the following cases:
- Contact with individuals infected with tuberculosis.
- Exposure to sick individuals, viruses, and bacteria (healthcare personnel).
- Symptoms consistent with tuberculosis (cough, weight loss, sweating).
- Chest X-ray with abnormalities.
- Weakened immune system.
- Individuals coming from countries with a high incidence of the disease.
How is it performed?
The tuberculosis test is done through a skin injection. A tuberculosis antigen (PPD) is injected superficially, and the body’s reaction is observed for two to three days.
It is common to mark the area where the PPD was injected with a pen to make it easier to detect a positive reaction.
After the specified time, the skin is checked, and the diameter of the area of inflammation at the injection point is measured. Only the indurated (raised) area is measured, not the reddened (erythema) area. Possible results:
- Slight redness without the formation of a bump: negative result.
- Bump smaller than 5 millimeters: negative result.
- Firm bump of 5 millimeters in individuals at risk (weakened immune system, substance abuse, diabetes, silicosis, chronic kidney disease, malnutrition): positive result.
- Firm bump of 10 millimeters in individuals at risk: positive result.
- Firm bump of 15 millimeters: positive result.
Despite this general guide, a definitive diagnosis requires additional tests and the evaluation of other factors by a doctor.
What happens if the result is positive?
Further tests should be performed to rule out an unknown active infection, including chest X-rays and sputum cultures. If active disease is present, treatment with multiple medications over an extended period will be required.
If no active infection is present, prophylaxis should be administered.
Risks
The risks of the Mantoux test are minimal; only some individuals experience a severe allergic reaction to the tuberculin. In these cases, pain and swelling occur in the area, and ulcers may even form.
There is no risk of contracting tuberculosis from the test itself, as the antigen does not contain live bacteria.
What to expect from the Mantoux test
The tuberculin test is an outpatient procedure, and normal activities can be resumed immediately afterward. On the day of the test, it is recommended to wear clothing that makes it easy to uncover the arm.
A mild sting is typically felt when the antigen is injected. Afterward, the ink mark around the inoculated area should not be covered or erased until returning to the appointment. If the test yields a positive result, redness, a rash, or a bump may appear on the arm.
Specialties that request the Mantoux test
The Mantoux test is typically performed by clinical analysis specialists, usually at the request of pulmonologists, family medicine practitioners, and internists.
How to prepare
The Mantoux test requires no prior preparation. There is no need to fast or take specific medications.
