TABLE 3.

Times to detection of mycobacteria^a

Organisms	System (no. of isolates detected)	Mean no. of days to detection (range)b			% Detected by day:
		All	Smear positivec	Smear negatived	7	14	21	28	35	42
All mycobacteria	BACTEC MGIT 960 (149)	13.1 (1–43)	10.5 (1–37)	14.8 (1–43)	31	67	83	90	95	99
	ESP II (166)	16.9 (2–45)	13.1 (2–33)	18.3 (2–45)	15	44	65	75	90	99
	Middlebrook agar (144)	19.2 (5–56)	16.6 (6–56)	21.0 (5–41)	7	28	71	87	93	99
MTBC	BACTEC MGIT 960 (55)	12.8 (5–26)	11.1 (5–26)	14.1 (5–22)	15	69	95	100
	ESP II (48)	18.7 (3–39)	15.1 (3–31)	24.4 (3–39)	6	27	69	83	98	100
	Middlebrook agar (57)	19.2 (6–56)	16.5 (6–56)	22.3 (8–40)	4	35	74	91	93	98

^aMedia were routinely incubated for 6 weeks; some cultures were incubated for up to 8 weeks due to special circumstances. 

^bDifference between BACTEC MGIT 960 and ESP II times to detection for those specimens positive for any mycobacteria and for MTBC by both systems was statistically significant (P < 0.05, Student's t test). 

^cNumbers of MTBC smear-positive specimens for BACTEC MGIT 960, ESP II, and Middlebrook agar were 27, 26, and 31, respectively. 

^dNumbers of MTBC smear-negative specimens for BACTEC MGIT 960, ESP II, and Middlebrook agar were 28, 22, and 26, respectively.