Which of the following accurately describes the current screening test used in the UK to check for TB exposure?

A) Blood culture.
B) Chest CT.
C) Chest x-ray.
D) A circle of needles punctures the forearm through which tuberculin is injected.
E) A quantity of tuberculin is injected intradermally.


The answer is E. This is known as the Mantoux test. The Heaf test [described in D] was previously used but is no longer. An individual will test positive to either skin test if they:

• Have active TB.
• Had TB in the past.
• Have had the BCG vaccine. 

Blood culture can take up to 8 weeks to show TB as it grows so slowly - each round of replication takes 24 hours.

Although CXR is commonly used to diagnose TB it is not routinely used to screen patients for TB exposure.