Comparison of four commercial quantitative HIV-1 assays for viral load monitoring in clinical daily routine.

Background: Quantification of viral load (VL) is standard for monitoring HIV-1 therapy and is crucial before deciding whether to switch or to continue a current antiretroviral regimen.

Methods: We compared the performance of the four most widely used commercial viral-load assays, COBAS Amplicor Monitor v1.5, Versant HIV-1 RNA 3.0, Abbott RealTime HIV-1 and Cobas AmpliPrep/Cobas TaqMan HIV-1 (CAP/CTM), in terms of intra- and inter-assay variability, as well as hands-on-time, specificity and ability to quantify group M subtypes.

Results: Although linearity and correlation were confirmed for the assays and comparable sensitivity and specificity were verified for genetically diverse HIV-1 subtypes, demonstrating suitability for monitoring of HIV group M isolates, the viral loads obtained showed variations, with a mean difference of 0.1-0.4 log, depending on the system used.

Conclusions: Although sensitivity and precision were confirmed for all the systems, differences between them should be taken into account when viral load monitoring of the same person is performed using different systems.