Mantoux Test (Tuberculin Skin Test)

            The Mantoux test is a screening tool for Tuberculosis (TB). It is also known as the Mantoux screening test, Tuberculin Skin Test, Pirquet test, Mendel-Mantoux test. Tuberculin is a glycerol extract of the tubercle bacillus. Purified protein derivative (PPD) tuberculin is a precipitate of species-nonspecific molecules obtained from filtrates of sterilized, concentrated cultures. The tuberculin reaction was first described by Robert Koch in 1890. The Test was first developed and described by the German physician Felix Mendel in 1908. The test is named after Charles Mantoux, a French physician who built on the work of Koch and Clemens von Pirquet to create his test in 1907.

Procedure
1. Supplies :
- Alcohol Swabs
- Tuberculin syringe with attached safety needle
- Vial of Tuberculin Purified Protein Derivative (PPD) solution.
Note: Keep solutions refrigerated at all times.
2. Administration of Mantoux Test :
- Check the label of the PPD vial for proper strength , expiry date and the date vial was opened (if applicable).
- Clean top of vial with an alcohol swab and let dry. Draw 0.1 ml (5 tuberculin units) into tuberculin syringe.
- Place the patient’s forearm palm side up on a firm, well-lit surface and select an area of healthy skin approximately 3 finger widths below the ante-cubital space. This area should be free of muscle margins, heavy hair, vein, sores or scars. Clean site with alcohol.
- Keeping the skin taut, hold the syringe almost parallel to the skin (at approximately 15
degrees) and insert needle with the bevel up into the superficial layer of skin until the
bevel is fully inserted and the tip is visible under the skin. Relax the skin and inject the
PPD. Resistance should be felt upon injection.
Note: A tight 6-10 mm wheal should form at the site of in sertion. If a wheal does not form, the injection was given too deep and must be repeated on the opposite arm. If a substantial portion of the dose leaks out of the injection site, the injection wasn’t given deep enough and must be repeated on the opposite arm.
- Do not press the site after injection to prevent displacement of the solution.
- Inform the patient that mild itching, swelling, or irritation may occur and these are normal reactions that do not require any treatment. Inform the patient to avoid scratching the site, keep the site clean and avoid putting creams, lotions, or adhesive
dressings on the site.
Note: The standard reading time of the test is 48-72 hours. However, induration of 10 mm or greater can be read at 6-24 hours and at 72-96 hours.

Mantoux (Tuberculin Skin Test)

Normal (negative results):	No firm bump forms at the test site, or a bump forms that is smaller than 5 mm (0.2 in.).
Abnormal (positive results):	A firm bump that is 5 mm (0.2 in.) in size shows a TB infection in people who are in a high-risk group.
	A firm bump that is 10 mm (0.4 in.) in size shows a TB infection in people who are in a moderate-risk group.
	A firm bump that is 15 mm (0.6 in.) in size shows a TB infection in people who are in a low-risk group.

False Positive Result
TST (Tuberculin skin test) positive is measured by size of induration. The measurement of the induration is determined to be positive depending on risk factors. For example, a low-risk patient must have a larger induration for a positive than a high-risk patient. High-risk groups include recent contact, HIV, chest radiograph with fibrotic changes, organ transplant recipient, and immunosuppression.

False Negative Result
The result of PPD or tuberculin test is suppressed by the following conditions :
1. Infectious mononucleosis
2. Live virus vaccine- The test should not be carried out within 3 weeks of live virus vaccination and should be rearranged.
3. Sarcoidosis
4. Hodgkin's disease
5. Corticosteroid therapy/Steroid use
6. Malnutrition
7. Immunologically compromised- Those on immuno-suppressive treatment or those with HIV and low CD4 T cell counts, frequently show negative results from the PPD test.
This is because the immune system needs to be functional to mount a response to the protein derivative injected under the skin. A false negative result may occur in a person who has been recently infected with TB, but whose immune system hasn't yet reacted to the bacteria.
8. Upper respiratory virus infection.