Seventeen (17) clinical plasma samples (obtained from NIH Blood Bank) from donors who tested positive for HIV-1, HBV, or HCV were used to evaluate the array sensitivity and specificity. The genome copy of each virus in virus-positive plasma samples was previously determined by the NIH Blood Bank using commercial assays approved for donor screening. Representative results from the testing of three HBV-positive plasma samples (pt.#13-pt.#15) using our array are shown on Figure 2 . The threshold cycle cut off of the assay performed with plasma samples was set up as C(t)#43 (see Materials and Methods). The wells with C(t) lower than the cut-off and the obtained Tm peaks within the expected Tm range indicate positive amplification of HBV target genes and are highlighted with blue circles (Figure 2 , green color code for HBV). For samples #13 and #14 Tm peaks of the products, obtained with only two HBV specific primer sets (wells G2, G3-pt.#13 and wells G5, G6-pt.#14), were within the expected range, with C(t) values of 36.7-42.9 and 36.5-36.6 respectively. For sample #15, all three HBV specific primer sets gave the Tm peaks within the expected range (wells G7, G8 and G9), and the C(t) values range was 33.8-34.2. The genome copy number of HBV in plasma samples #13-15 was 151-518 copies/ ml, corresponding to 6-21 copies/PCR. The wells (white color code, red circles) with the human beta-globin gene specific primer set, serving as the internal control, produced positive signals from all three plasma samples tested, with C(t) values of 25.5-26.3 (wells H3, H6 and H9 - Figure 2 ), which shows that the quality of the RNA/DNA sample preparation was equally good for the plasma of these three patients.