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Case 5: A 32-Year-Old with Chronic Cough

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C The patient’s small tuberculin skin test reaction is probably due to prior BCG vaccination, and an alternative diagnosis should be sought.

This answer is incorrect. Induration of 5 mm or greater is considered positive in any HIV-infected person. This cut-point is used for individuals who are at high risk for progression to active tuberculosis if infected with Mycobacterium tuberculosis, a group that includes HIV-infected individuals. Prior receipt of the BCG vaccine is irrelevant in interpreting tuberculin skin test results.

A If a nucleic acid amplification test on sputum is positive for Mycobacterium tuberculosis, sputum culture is not required.
B If the pleural effusion is tapped, there is greater than 80% likelihood that a Ziehl-Neelsen stain of pleural fluid will show AFB.
D Therapy for TB should be initiated while the diagnostic work-up continues.
E The patient’s CD4 cell count is almost certainly less than 100 cells/mm3.

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