Table 1.

Comparison of IFA and the alamarBlue assay for enumeration of C. trachomatis infection

Dilution of EB	Infection level (%) 24 hpi in IFA	Reducing capability of infected cells relative to the mock-infected cellsa
		24 hpi			48 hpi			72 hpi
		Avg (%)	SD (%)	Z′ factor	Avg (%)	SD (%)	Z′ factor	Avg (%)	SD (%)	Z′ factor
1:1	95.77	26.40	1.36	0.56*	6.90	0.68	0.83*	4.21	0.08	0.98*
1:2	92.94	61.80	3.66	−0.02	18.83	0.89	0.79*	6.13	0.28	0.97*
1:4	90.64	87.84	4.71	−2.47	46.35	0.27	0.72*	13.42	1.59	0.92*
1:8	86.70	103.00	6.16	−14.50	69.27	0.78	0.47	27.96	2.17	0.88*
1:16	63.95	107.29	2.15	−3.74	85.86	2.26	−0.47	49.17	2.91	0.79*
1:32	43.61	109.90	5.82	−3.60	96.11	1.15	−3.50	74.03	2.82	0.60*
1:64	20.80	114.35	4.43	−1.88	106.17	0.42	−1.48	85.67	1.35	0.57*
1:128	14.79	119.60	9.48	−1.88	99.23	5.43	−38.28	88.67	2.00	0.29
1:256	7.20	114.30	0.77	−1.13	102.47	0.49	−5.27	100.06	0.72	−75.83
1:512	3.06	108.15	8.51	−5.58	105.74	0.61	−1.76	100.58	0.47	−4.98
1:1,024	2.16	102.65	4.24	−14.41	103.46	1.90	−4.71	102.67	2.49	−2.57
1:2,048	1.08	120.76	8.34	−1.56	108.26	0.66	−0.94	103.06	0.50	−0.17
1:4,096	0.98	109.81	0.48	−2.01	108.17	2.61	−1.67	105.87	0.66	0.31
R2		0.52			0.79			0.98

^aZ′ factors of <1 and ≥0.5 (marked with asterisks) are indicative of an assay with suitable screening characteristics (14). SD, standard deviation.