Evaluation of a new real-time PCR assay kit for quantification of human immunodeficiency virus RNA in plasma

We evaluated the use of COBAS TaqMan HIV-1 for highly pure system (COBAS TaqMan) recently developed as a second-generation quantification of human immunodeficiency virus type 1 (HIV-1) RNA. The linearity, sensitivity, reproducibility, and effects of possibly interfering materials were examined and results compared to those of AMPLICOR HIV-1 MONITOR Test version 1.5 (AMPLICOR) using 6 virus isolates that were all different subtypes. Excellent linearity was obtained at 1.67 x 10(2)-1.73 x 10(6) copies/mL (r2 = 0.991). Sensitivity was 40 copies/mL at a 100% hit rate. Intraexperimental CVs were 27.4-50.8%, and interexperimental CVs were 29.3-81.5%. Although COBAS TaqMan showed an excellent titer correlation with AMPLICOR (r2 = 0.960), mean titer obtained with COBAS TaqMan was 3.1 times higher than that with AMPLICOR (p = 0.002), and 7.1 times higher in a sample of subtype C, suggesting discrepancies in HIV-1 RNA quantification between the two kits. This point should be noted when AMPLICOR is replaced by COBAS TaqMan.