Another assessment of detection sensitivity in relation to smear positivity and CFU was performed with 24 seeded specimens. Cell concentrations equivalent to 103, 10 4, and 105 dilutions of a 0.5 McFarlandstandard yielded smear results of 1,doubtful/borderline (1 to 3 AFB per 100 fields at 400 magnification), and negative, respectively. The specimens with positive smear results yielded 100% sensitivity and correct sequences in each subassay. The smear-negative specimens yielded 80 to 240 CFU/ml and 100% sensitivity (8/8 specimens) in the IS6110, inhA, and rpoB subasay