A male client is asking the nurse a question regarding the Mantoux test for tuberculosis. The nurse should base her response on the fact that the:
A. Area of redness is measured in 3 days and determines whether tuberculosis is present.
B. Skin test doesn’t differentiate between active and dormant tuberculosis infection.
C. Presence of a wheal at the injection site in 2 days indicates active tuberculosis.
D. Test stimulates a reddened response in some clients and requires a second test in 3 months.
Correct Answer: B. Skin test doesn’t differentiate between active and dormant tuberculosis infection.
The Mantoux test doesn’t differentiate between active and dormant infections. If a positive reaction occurs, a sputum smear and culture as well as a chest X-ray are necessary to provide more information. According to CDC, this test is performed using the ‘Mantoux technique,’ which is injecting 0.1 mL of a solution containing 5 units of tuberculin purified protein derivative into the inner surface of the forearm through the intradermal route. It should be administered two or more than 2 inches from the elbow, wrist, or any other injection site.
Option A: Although the area of redness is measured in 3 days, a second test may be needed; neither test indicates that tuberculosis is active. It is a time-sensitive test. Tests that are read late are not accurate as they tend to under-estimate the size of the skin reaction. Therefore, the reliability of the test is compromised, and the results are doubtful. To avoid this, repeat testing is recommended if the reaction is not read on time.
Option C: The presence of a wheal within 2 days doesn’t indicate active tuberculosis. Type IV hypersensitivity reaction (delayed-type) to the injected tuberculin PPD antigen is seen and measured. The reaction starts at 5 to 6 hours, with a peak effect at 48 to 72 hours, after which it begins to subside. Therefore, the right time to read the test is after 48 to 72 hours of intradermal test placement.
Option D: In the Mantoux test, an induration 5 to 9 mm in diameter indicates a borderline reaction; a larger induration indicates a positive reaction. Induration is the palpable, raised swelling, which is measured transversely by inspection and palpation.
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