Procedure
A standard dose is 5 tuberculin units (TU - 0.1 ml) (The standard Mantoux test in the UK consists of an intradermal injection of 2 TU of Statens Serum Institute (SSI) tuberculin RT23 in 0.1 ml solution for injection.) is injected intradermally (between the layers of dermis) and read 48 to 72 hours later. This intradermal injection is termed the Mantoux technique. A person who has been exposed to the bacteria is expected to mount an immune response in the skin containing the bacterial proteins.
The reaction is read by measuring the diameter of induration (palpable raised, hardened area) across the forearm (perpendicular to the long axis) in millimeters. If there is no induration, the result should be recorded as "0 mm". Erythema (redness) should not be measured.
If a person has had a history of a positive tuberculin skin test, or had a recent tuberculin skin test (within one year), another skin test should be used.
Read more about this topic: Mantoux Test