TABLE 3.

Reproducibility of phenotypic resistance testing in the MT4-MTT cell viability assay^a

Sample no. and drug	IC50 (μM)							Fold resistanceb
	Determin. 1	Determin. 2	Determin. 3	Determin. 4	Mean	SEM (n = 4)c	CVd	Determin. 1	Determin. 2	Determin. 3	Determin. 4	Mean	SEM (n = 4)	CV
10
AZT	13.6	3.70	6.50	12.5	9.1	2.38	0.26	211	79	137	192	155	30	0.19
Tivirapine	0.47	0.32	0.44	0.51	0.4	0.04	0.09	30	23	31	37	30	3	0.09
Loviride	0.31	0.28	0.36	0.41	0.3	0.03	0.08	8	9	11	8	9	1	0.08
ddI	8.10	8.20	8.70	12.8	9.5	1.12	0.12	1	2	2	2	2	0.3	0.14
ddC	7.50	8.30	8.90	9.20	8.5	0.37	0.04	2	2	3	3	3	0.3	0.12
d4T	10.0	3.20	5.40	9.20	7.0	1.60	0.23	2	2	3	3	3	0.3	0.12
3TC	>100	>100	>100	>100	>100	NDe	ND	>17	>10	>10	>13	>12	ND
20
Indinavir	0.15	0.63	0.42	0.26	0.4	0.10	0.29	18	8	12	6	11	3	0.24
Ritonavir	0.56	1.71	1.72	0.38	1.1	0.36	0.33	22	20	21	10	18	3	0.15
Saquinavir	0.23	0.37	0.40	0.15	0.3	0.06	0.20	82	37	71	21	53	14	0.27

^aThe PR and RT inhibitor resistance profiles were determined for four different recombinant viruses separately generated from the same plasma sample (sample 10 or 20). The profiles of the susceptibilities of the respective viruses to seven RT inhibitors (sample 10) and three PR inhibitors (sample 20) are expressed as IC₅₀s and as the means of these determinations (Determin.). The same results are also expressed as fold resistance values. 

^bFold increase in the mean IC₅₀ relative to the mean IC₅₀ for the wild type. The mean IC₅₀ for both viruses from patients and wild-type viruses is derived from two to four separate susceptibility determinations by the MT4-MTT assay. 

^cSEM, standard error of the mean. 

^dCV, coefficient of variation. 

^eND, not determined.