The four HIV-1 specific primer sets were further evaluated by testing them against another FDA/CBER analytical panel containing a broad spectrum of HIV-1 subtypes. As summarized in Table 3 , the HIV-1 subtype F (group M) and group O isolates in Table 2 . The results of sensitivity testing of the real-time PCR array primer sets specific for HIV-1, HIV-2, HBV, HCV, and WNV the with FDA/CBER analytical plasma panels. Table 3 . Sensitivity of four HIV-1 specific primer sets selected for the real-time PCR array in testing with FDA/CBER analytical HIV-1 broad spectrum panel. Detection limit (copy number/ml of plasma) was evaluated using FDA/CBER analytical panel, containing pre-set copy number of HIV-1 spiked into 1 ml of ''normal'' human plasma. RNA from 1 ml of plasma was converted to cDNA and divided into eight PCR reactions; two PCR repeats were performed for each primer set. The estimated copy number per PCR reaction is shown in parentheses. the panel could not be successfully amplified by any of the four selected primer sets (detection limit is .1,000 RNA copy/ml of plasma). All other subtypes and CRFs of group M, and the group N isolate could be amplified with at least one out of the four primer sets at 50 to 1,000 RNA copies/ml of plasma (Table 3) . The Tm peaks of the PCR products amplified from different subtypes of HIV-1 varied within 1.5uC ( Table 3 ). All of the four selected HIV-1 specific primer sets amplified HIV-1 subtype B (group M) with the highest sensitivity (50-500 copies/ml of plasma).