Final answer:
The Mantoux tuberculin skin test is an intradermal test for TB exposure, resulting in an induration as a positive response, which might also occur due to BCG vaccination.
Step-by-step explanation:
The test you're referring to is the Mantoux tuberculin skin test, which is administered by injecting a small amount of tuberculin intradermally, usually in the inside of the forearm.
This test is used to determine if a person has been exposed to tuberculosis (TB), indicated by a delayed hypersensitivity reaction.
A positive result, seen as a raised red area known as an induration, implies an immune response to the bacteria but does not necessarily mean active TB infection is present.
The Mantoux test evolved from earlier methods such as the scarification technique devised by Clemans von Pirquet.
He made multiple punctures in the skin to introduce the tuberculin antigen, but this method was later modified by Mantoux for a single injection, improving the test's safety and reliability.
While the induration could suggest prior exposure, in areas where the bacillus Calmette-Guérin (BCG) vaccine is commonly administered, a positive Mantoux test might not specifically indicate TB due to vaccine-induced immunity.
Given that a positive tuberculin test could result from either a past TB infection or BCG vaccination, additional diagnostic tools such as chest radiographs might be necessary to confirm TB exposure and distinguish it from a vaccine response, especially where BCG is part of the routine vaccination program.