TABLE 2.

Real-time PCR intra- and interassay variability^a

Input copy no. per ml of blood	Observed copy no.
	Intra-assay (n = 4)b	Interassay (n = 4)c
0	0	0
494	458 ± 22 (5)	521 ± 118 (23)
1,482	1,481 ± 426 (29)	1,445 ± 398 (28)
4,444	4,495 ± 1,226 (27)	4,914 ± 1,032 (21)
13,333	12,128 ± 4,594 (38)	11,776 ± 1,928 (16)
40,000	40,549 ± 3,462 (9)	44,309 ± 8,433 (19)

^aA standard panel of DBS with the numbers of 8E5 cells from 0 to 40,000 copies per ml of HIV-1-negative blood (3× serial dilutions) was prepared and extracted as described in Materials and Methods. For the intra-assay determination, DNAs from 24 samples (4 panels each with 6 spots with different 8E5 content) were extracted and then run in the same real-time assay. For the interassay determination, DNA samples from the panel were isolated in four separate extraction runs and then assayed in four separate real-time assays. Results are given as means±one standard deviation; coefficients of variation (%) are given in parentheses.

^bProviral DNA number was determined by the dC_T standard curve as described in the legend for Fig. 2C.

^cdC_T-based standard curve was constructed for each interassay run.