16th International AIDS Conference Toronto, Canada - August 13 - 18, 2006

EVALUATION OF THE CAVIDI EXAVIR™ LOAD QUANTITATIVE HIV RT LOAD IT AS AN ALTERNATIVE HIV VIRAL LOAD MONITORING TEST FOR USE IN RESOURCE-CONSTRAINED SETTINGS

Int Conf AIDS. 2006 Aug 13-18;16 Abstract No. TuAb0204

V. Greengrass, P. Steele, M. Plate, L. Morris, S. Crowe
Burnet Institute, Clinical Research Laboratory, Melbourne, Australia

BACKGROUND: Widely used molecular biology based viral load assays for monitoring HIV are not technically or economically feasible in most resource-constrained settings. With increasing availability of affordable antiretroviral drugs, there is a growing need for less expensive and simpler tests to monitor HIV disease progression in resource-constrained areas in order to provide appropriate monitoring of antiretroviral therapy.

We evaluated version 2 of a low cost manual reverse transcriptase assay, ExaVir™ Load assay Cavidi Tech (HIV RT), against a commercial HIV RNA viral load assay to assess its potential use to monitor HIV infection in resource-constrained settings.

METHODS: Frozen plasma samples from HIV-infected individuals previously quantified for HIV RNA using the COBAS Amplicor HIV-1 Monitor assay, ultra-sensitive preparation (RT-PCR), were retested for HIV RT activity. Plasma from ten patients was also tested in varying dilutions to determine whether the RT assay could test smaller volumes of plasma.

RESULTS: The HIV RT assay showed good sensitivity with detectable HIV RT in 93% of samples (n=121) with HIV RNA >1,000 copies/ml and 73% (n=33) between 401 – 1000 copies/ml. A positive association was found between the HIV RNA copies/ml and HIV RT copies/ml equivalents (r=0.96; n=182). A decrease in association was observed when samples <2000 copies/ml were analysed (r=0.35; n=89). Ten samples were tested on the same HIV RT assay using plasma input volumes of 1ml (recommended), 0.5ml and 0.25ml and compared to HIV RNA. All dilutions differed from the matched HIV RNA test by <0.32 log₁₀. The HIV RNA results for each patient were reproducible using different volumes with variation for all patients <0.42 log₁₀.

CONCLUSIONS: The HIV RT assay showed good association with the RT-PCR assay, and has sensitivity approaching that of RTPCR. The HIV RT assay was reproducible using smaller sample volumes making it useful for paediatric testing.

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2006-08-13
TuAb0204

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