Question

• lipsky ba, et al. factors affecting the clinical value of microscopy for acid-fast bacilli. rev infect dis. 1984; 6: 214-222.

Answer 1

In order to assess the clinical value of microscopy for acid-fast bacilli (AFB), the results of 3,207 clinical specimens submitted for mycobacterial smear and culture were analyzed. Mycobacteria grew from 176 (5.5%) of the specimens, 95 (54%) of which were Mycobacterium tuberculosis. Although the overall sensitivity of the smear was low (33%), 65% of respiratory specimens yielding M. tuberculosis had positive AFB smears. Furthermore, 96% of patients with pulmonary tuberculosis from whom more than one specimen was processed had at least a single positive AFB smear. Smear sensitivity correlated well with quantitative growth; 89% of specimens yielding greater than or equal to 50 colonies per slant were smear positive.
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