Assay of plasma samples representing different HIV-1 genetic subtypes: An evaluation of new versions of the Amplicor HIV-1 monitor assay

Quantification of plasma HIV-1 RNA levels has rapidly become the main tool for monitoring disease progression and treatment. However, some first-gener ation assays do not accurately quantify all HIV-1 subtypes, This study comp ares the first-generation and two newer prototype Amplicor HIV-1 Monitor as says (Roche Diagnostic Systems) in terms of their performance in quantifyin g HIV-1 RNA in stored plasma samples from 101 individuals infected with var ious genetic subtypes of HIV-1 (28 subtype A, 18 B, 26 C, 20 D, 2 E, 3 G, 2 H, and 2 J), The HIV-1 subtype had previously been determined by direct se quencing of the V3 domain of the env gene. The results from the three assay s agreed for subtypes B and C, as well as for most subtype D samples. In co ntrast, the first-generation assay reported significantly lower plasma HIV- 1 RNA levels than did the two newer versions of the assay for most subtype A, E, G, and H samples. There were no differences in mean plasma HIV-1 RNA levels between individuals infected with subtypes A, B, C, and D if the res ults from the two newer test versions were used, and if an adjustment was m ade between subtypes for differences in CD4 count. Thus, this study confirm s that the first-generation assay does not accurately quantify HIV-1 RNA le vels in many individuals infected with subtype A, E, G, and H, These proble ms appeared to have been greatly reduced in the two new prototype versions.