Tuberculosis can be diagnosed from a ____.

Tuberculosis can be diagnosed from a ____.

• A. Blood culture
• B. Sputum specimen
• C. Urine sample
• D. Fecal sample

Answer: (B)

Tuberculosis in the lungs sheds organisms into the airways, so collecting a sample of respiratory secretions—sputum—provides the most direct and reliable material to test for the bacteria. Sputum can be examined under a microscope for acid-fast bacilli, cultured to grow Mycobacterium tuberculosis, or tested with rapid molecular methods, all of which are standard ways to confirm active pulmonary TB. Because the bacteria are not consistently present in large numbers in blood, urine, or stool for routine pulmonary TB, those samples are far less useful for initial diagnosis. Blood cultures may detect disseminated TB only in more rare, widespread cases, not typical pulmonary TB, and urine or fecal samples don’t reliably reflect pulmonary infection.

Tuberculosis in the lungs sheds organisms into the airways, so collecting a sample of respiratory secretions—sputum—provides the most direct and reliable material to test for the bacteria. Sputum can be examined under a microscope for acid-fast bacilli, cultured to grow Mycobacterium tuberculosis, or tested with rapid molecular methods, all of which are standard ways to confirm active pulmonary TB. Because the bacteria are not consistently present in large numbers in blood, urine, or stool for routine pulmonary TB, those samples are far less useful for initial diagnosis. Blood cultures may detect disseminated TB only in more rare, widespread cases, not typical pulmonary TB, and urine or fecal samples don’t reliably reflect pulmonary infection.