what is the mantoux screening test/ pirquet test?
The Mantoux test or Pirquet test or PPD test for purified protein derivative is a skin test that is used to diagnosis if someone has tuberculosis. The basis of the reading of this test is to identify the presence or absence of the amount of induration (localised swelling). It is used to determine if someone has developed an immune response to the bacteria that causes TB. The test is based on the fact that the bacteria which causes Tuberculosis, i.e. Mycobacterium Tuberculosis produced a delayed hypersensitivity skin reaction to the pirquet test to certain components of the bacterium
A Tb Mantoux test results may sometimes be negative, but that does not always mean that a person is free of tuberculosis. This is mainly because sometimes if a person is exposed to the bacteria, there is an incubation period of two to twelve weeks for the PPD test to be positive.
why do i need this test?
A Mantoux test is a skin test that is used to detect infection by Mycobacterium Tuberculosis (TB). It is used to determine any immune response in the skin, by any individual who could have been or is being exposed to the bacteria.
If you are experience one or many of the below-mentioned symptoms, you have to take the Pirquet test to determine if you are positive for Mycobacterium tuberculosis.
1. Night Sweats
2. Inexplicable weight loss
6. Loss of appetite
7. Prolonged and persistent cough
8. Blood in sputum
9. Painful breathing
10. Painful coughing
When tuberculosis is severe, it spreads to the lungs, and you can see the following Manquet test positive symptoms
1. Chest pain
2. Coughing blood
3. Prolonged cough for more than three weeks
what other tests might i have along with this test?
If the Mantoux results are positive, then the doctor will ask for blood tests or X-ray of your chest. Also there could also be tests to check for infection through your sputum. Finally, urine or tissue samples can also be collected for testing if the doctor has diagnosed that the infection is spreading.
what do my test results mean?
The diagnosis usually occurs in two phases. Once the injection is given, and the induration appears the second stage needs to be initiated within 24-48 hours of giving it. The doctor will check to see what has happened to the bump of the skin. The Mantoux test results are interpreted by the induration size (in diameter) which occurs in addition to certain specific risks factors associated with the patient. Mantoux test positive symptoms are detected in a healthy person if the induration is greater than or equal to 15mm. The Mantoux test positive is absolute if blisters are present while interpreting.
Here is an indicative reference range that is used by the healthcare professionals to interpret the results of the Mantoux test measurement for results.
how is this test done?
A Mantoux screening is conducted by giving an injection of 0.1 mL of a liquid containing 5 TU (tuberculin units) of PPD into the topmost layer of skin (i.e. intradermal) which is the layer under the surface of the skin of the forearm. Tuberculin is a fraction of the purified protein taken from the bacteria that causes Tuberculosis, i.e. Mycobacterium tuberculosis. Generally, it is given in an area of the skin where there are no abnormalities and far away from the veins.
If the injection is done properly, a pale and discrete elevation of the skin (6mm-10mm) in diameter should appear. Mantoux test positive treatment is administered by the doctor if diagnosed where special medication is prescribed for 6 to 9 months.
does this test pose any risk?
Some of the common side effects of the pirquet or Mantoux test side effects swelling, itching or tenderness at the site of the injection which not continue beyond a week.
what might affect my test results?
People who live in high-risk areas or those who have come in contact with a person who has TB are at a higher risk of contracting the disease. The other variables which may affect the test results are
1. Working in a medical facility where you come in contact with infected patients or children
2. Having TB in the past
3. HIV positive
4. Drug users especially injected
5. Having an organ transplant
6. Very young children are also at a higher risk
7. Pregnant women
There is no blood or urine sample required for the test. The only sample collection procedure involves injecting PPD (tuberculin units)into the forearm of the patient. It is recommended to give 5 TU for children and 10 TU for adults.
how do i prepare for the test?
To take up the Mantoux screening test, no fasting is required. Also, no other special preparations are always required for the test. Maintain a healthy lifestyle with proper nutrition and please inform the doctor of all the medication you are having and any items herbs, food items, drugs you may be allergic to.
Understanding results of Mantoux Screening
|5 to 9 mm||Equivocal|
|(Diameter of Induration)0 to 4 mm||Negative|
|10 mm and above||Positive|
‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges'
If you are concerned about your cough or fever has been persistent, then it is better to get a TB Mantoux test results to ascertain your infection. Most hospitals and clinics provide the Mantoux test cost at a reasonable rate, and it can be done over the course of 3 days.