Final answer:
The preferred TB testing method for a patient with a history of BCG vaccination is TB blood tests (IGRAs), which do not yield false-positive results like the Mantoux tuberculin skin test can in such cases.
Step-by-step explanation:
The preferred method of tuberculosis (TB) testing for a patient who has previously received the Bacillus Calmette-Guerin (BCG) vaccine is TB blood tests (Interferon-Gamma Release Assays or IGRAs). IGRAs are favored because the BCG vaccine can cause false-positive results in the Mantoux tuberculin skin test, which is another method for TB testing. This is due to the BCG vaccine's ability to evoke a positive reaction in a tuberculin skin test by stimulating a delayed-type hypersensitivity response, which reflects a historical exposure to TB antigens, rather than an active TB infection. In the United States, where the BCG vaccine is not routinely used, the Mantoux test can still be indicative of TB exposure. However, for those who have been vaccinated with BCG, typically in countries with a higher prevalence of TB, the Mantoux test's usefulness is compromised. Therefore, IGRAs are the recommended test to discriminate between BCG vaccination and TB infection in a patient with a history of BCG vaccination.