TABLE 2.

PER SITE CORRELATION BETWEEN MYCOBACTERIUM TUBERCULOSIS CYCLE-THRESHOLD AND CONVENTIONAL DIAGNOSTIC TECHNIQUES

			rs Internal Control Ct <34		N Internal Control Ct Ct >34	% Internal Control Ct Ct >34	AFB Smear Grade
Method	Site	rs*		N			3+	2+	1+	Scanty	Negative
AFB smear (pellet)	A	−0.77	−0.83	397	69	17.4	154	59	126	50	8
	B	−0.83	−0.86	247	30	12.1	31	30	55	25	106
	C	−0.72	−0.77	260	31	11.9	60	35	56	23	86
	D	−0.59	−0.68	349	86	24.6	185	49	43	10	62
	E	−0.55	−0.57	80	10	12.5	27	12	16	2	23
	Total	−0.69	−0.77	1,333	226	17	457	185	296	110	285
AFB smear (sputum)	A	−0.71	−0.76	201	21	10.4	48	20	79	36	18
	B	−0.81	−0.83	123	12	9.8	10	12	24	14	63
	C	−0.69	−0.73	136	19	14	5	20	31	13	67
	D	−0.55	−0.70	179	30	16.8	82	34	25	3	35
	E	−0.65	−0.62	36	4	11.1	8	11	7	2	8
	Total	−0.63	−0.71	675	86	12.7	153	97	166	68	191
							Solid Culture CFU Grade
							3+	2+	1+	<20 CFU	Negative
LJ solid culture†	A	−0.41	−0.46	397	69	17.4	71	126	173	21	6
	B	−0.71	−0.73	187	24	12.8	50	40	44	47	6
	C	−0.56	−0.60	220	29	13.2	97	40	43	23	17
	D	−0.54	−0.50	154	36	23.4	4	49	39	33	29
	Total	−0.53	−0.56	958	158	16.5	222	255	299	124	58
							MGIT Time to Detection (days)
							1–28	>28	Negative
MGIT liquid culture†‡	A	0.56	0.66	397	71	17.9	387	4	6
	B	0.77	0.77	218	25	11.5	214	0	4
	C	0.73	0.78	235	30	12.8	214	15	6
	D	0.49	0.66	160	42	26.3	155	3	2
	Total	0.67	0.68	1,010	168	16.6	970	22	18

Definition of abbreviations: AFB = acid-fast bacilli; Ct = cycle-threshold; LJ = Löwenstein–Jensen agar slants; MGIT = mycobacterial growth indicator tube.

^*Spearman rank correlation coefficient.

^†Site E used alternative solid media (Middlebrook 7H11), and liquid culture time-to-detection was not recorded at this site.

^‡Excluding MGIT cultures with TTD greater than 28 days.