A 45-year-old traveler discovers that he has converted from negative to positive on the tuberculin (PPD) skin test. This indicates which of the following?
|A||He has active tuberculosis.|
|B||He has delayed-type hypersensitivity against Mycobacterium tuberculosis.|
|C||He is most likely to be infected with an "atypical" Mycobacterium.|
|D||He needs to immediately isolated to prevent spread of M. tuberculosis|
a. The purified protein derivative (PPD) skin test, or tuberculin skin test, contains several proteins from M. tuberculosis, which when combined with waxes elicits a delayed hypersensitivity.
b. It does not assess for the status of infection, but only speaks about prior exposure. The clinical presentation and/or chest radiograph would be the next steps in evaluation.