My son is going abroad on work placement as part of his university course. The hospital, where he will be working, has asked for documentary evidence that he has had a “two-step Mantoux skin test” within the past 12 months.
What is this test for and what does this involve?
The Mantoux tuberculin skin test is a method of determining whether a person is infected with Mycobacterium tuberculosis (TB).
The test is performed by injecting a small quantity of tuberculin purified protein derivative (PPD) under the skin. The usual site for the test is on the inner surface of the forearm. The procedure typically produces a pale elevation of the skin 6-10mm in diameter.
Between 48 and 72 hours after the initial administration of the PPD, the skin is inspected for a reaction. The reaction, a palpable, raised, hardened area or swelling, rather than any redness produced, is measured in millimetres.
The size of a positive test result depends on the exposure history and health status of the individual. If the individual does not return to the doctor to have the test site examined within 72 hours, the test will have to be repeated.
A Mantoux test may be required as part of immigration requirements for some countries, in healthcare workers or in aid agency staff working in developing countries.
It may also be performed as part of TB screening and vaccination programmes.
Giving a second Mantoux test after an initial negative reaction is called two-step testing.
This is often used for the initial skin testing of adults who are going to be retested periodically, such as healthcare workers or nursing home residents.
This two-step approach can reduce the likelihood that a boosted reaction to a subsequent TB skin test will be misinterpreted as a recent infection.
Both tests usually need to be completed within a four-week period to count as a two-step test.
Can he have the test done if he is also receiving other vaccinations?
If additional vaccines are required, Mantoux testing is usually done either on the same day as vaccination with live-virus vaccine or four-six weeks after the administration of the live-virus vaccine, so as not to interfere with a test reaction.
Mantoux testing should be carried out at least one month after smallpox vaccination.
