Case:

In early July a 34-year-old infected male housed in a state correctional facility was taken to the prison hospital with a two-week history of fever, abdominal pain, and cough.  His chest radiograph was normal, and sputum samples were negative for acid-fast bacteria. The inmate was returned to the prison in mid-July without a definitive diagnosis.  In mid-August the male was examined at a community hospital. His sputum was positive for acid-fast bacteria, and he was diagnosed with active TB.  Later that year the medical student who examined the inmate also developed primary TB.

Further investigation identified 31 former and current inmates of the correctional facility also having signs and symptoms of active TB. The median age was 36, and all were infected with HIV.

• What is the tuberculin skin test? What does it measure and how (molecular mechanisms), and how are the results read?
• What tests might follow a positive tuberculin skin test in diagnosing TB?  What circumstances might yield a false-positive tuberculin test (molecular mechanism)
• Explain how a person's HIV status influences the risk of developing TB.
• Can HIV status influence tuberculin test results?