Assessment of the low-cost Cavidi ExaVir Load assay for monitoring HIV viral load in pediatric and adult patients

Abstract

Background: Viral load (VL) is a critical marker for monitoring HIV disease progression and response to antiretroviral therapy. In resource-constrained settings, there is a need for a simple and inexpensive assay to monitor infected adults and children.

Methods: We compared versions 2 and 3 of the ExaVir Load assay, Cavidi AB (HIV RT) with the Roche, COBAS Amplicor HIV-1 Monitor assay (HIV RNA) for quantifying HIV VL.

Results: The HIV RT version 2 assay showed good sensitivity with detection in 94% of samples with HIV RNA >1000 copies per milliliter. Adult samples were tested using HIV RT version 2 (n = 35) and version 3 (n = 23) assays with plasma volumes of 1 mL (recommended), 0.5 mL and 0.25 mL in comparison with HIV RNA. The HIV RT and HIV RNA assay results were comparable when tested using different volumes. Comparison of results from pediatric samples (n = 27), tested using 1 mL and a smaller volume by HIV RT version 2 were not significantly different.

Conclusions: The HIV RT assay was comparable to the HIV RNA assay with sensitivity approaching that of HIV RNA. Smaller volumes than the recommended 1 mL can be used, improving utility of this assay for pediatric monitoring.

Figure 1

HIV viral load results using different plasma volumes from 35 adult HIV+ patients tested using the HIV RT assay version 2 (a) and version 3 (b). HIV RNA values are shown using +. HIV RT values using the recommended 1 ml of plasma are shown using ●, 0.5ml plasma results using ◐ and 0.25 ml plasma results using ○. Samples shown in grey are below the detection limit of the HIV RT assay and have been assigned the assay detection limit.

Figure 2

HIV viral load results using different plasma volumes from 27 pediatric HIV+ individuals tested using the HIV RT assay version 2. HIV RT results using the larger volume of plasma (range: 1 to 0.3ml) are shown in dark grey and the smaller volume (range: 0.15 to 0.5ml, adjusted for dilution factor) are shown in light grey, * Results from 1ml plasma tested (n=6) as the recommended sample volume.