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

Question | Discussion | References | CME Credit

You answered:

	If a nucleic acid amplification test on sputum is positive for Mycobacterium tuberculosis, sputum culture is not required.

This answer is incorrect. A positive nucleic acid amplification test on the patient’s sputum would help make a rapid diagnosis of TB, but the evaluation of all cases of suspected TB should include a sputum culture, both to confirm the diagnosis and to perform drug susceptibility testing. Although nucleic acid amplification testing has excellent specificity for M. tuberculosis (98-99%), it has a reported sensitivity of only 40-80% on smear-negative specimens.

Choose another answer:

	If the pleural effusion is tapped, there is greater than 80% likelihood that a Ziehl-Neelsen stain of pleural fluid will show AFB.
	The patient’s small tuberculin skin test reaction is probably due to prior BCG vaccination, and an alternative diagnosis should be sought.
	Therapy for TB should be initiated while the diagnostic work-up continues.
	The patient’s CD4 cell count is almost certainly less than 100 cells/mm³.

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