The significance of HIV viral load assay precision: a review of the package insert specifications of two commercial kits

Abstract

Quantification of HIV-1 RNA levels is a vital tool in the medical management of individuals infected with HIV. The commercially available US Federal Drug Administration (FDA)-approved assays vary in their ability to accurately measure and detect significant changes in plasma viral load. A more precise assay can accurately distinguish true clinically significant biologic changes in viral plasma load from background noise, or systematic variation. These differences in precision between assays are profound at low, near-cutoff levels, but also occur throughout the dynamic range of the assays. This review examines the precision specifications, expressed as fold changes in test and retesting, across the dynamic ranges of the Bayer Versant bDNA assay, and the two available versions of the Roche Amplicor Monitor PCR assays. Highly validated data from their respective package inserts are analyzed to confirm each assay's performance throughout its dynamic range. The precision of a viral load assay is critical to patient management, and gives the clinician a clearer picture of the patient's true virologic status that is attributable to infection or treatment as opposed to systematic variation in assays.