Modification of the Abbott RealTime assay for detection of HIV-1 plasma RNA viral loads less than one copy per milliliter

San Francisco VA Medical Center, San Francisco, CA 94121, USA.
Journal of virological methods (Impact Factor: 1.78). 08/2011; 175(2):261-5. DOI: 10.1016/j.jviromet.2011.04.015
Source: PubMed


Although commercial tests are approved for detection of HIV-1 plasma viral loads ≥ 20 copies per milliliter (ml), only one specialized research assay has been reported to detect plasma viral loads as low as 1 copy/ml. This manuscript describes a method of concentrating HIV-1 virions from up to 30 ml of plasma, which can be combined with a commercial viral load test to create a widely available, reproducible assay for quantifying plasma HIV RNA levels less than 1 copy/ml. Using this pre-analytically modified assay, samples with a known level of 0.5 copy/ml were detected in 8 of 12 replicates (mean 0.47 copy/ml; 95% confidence interval (CI) 0.14-0.81 copy/ml) and samples with a known level of 1.0 copy/ml were detected in 13 of 13 replicates (mean 1.96 copy/ml; 95% CI 1.42-2.50 copy/ml). By concentrating virus from 30 ml of plasma, HIV RNA could be measured in 16 of 19 samples (84%) from 12 of 12 subjects (mean 2.77 copy/ml; 95% CI 0.86-4.68 copy/ml). The measured viral load correlated inversely (r = -0.78; p = 0.028) with the total duration of viral suppression (viral load<40 copies/ml).

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Available from: Joseph K Wong, Jun 17, 2015
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    • "Studies investigating patient outcome when residual viraemia is detected were published, as well as intensification trials exploring the effect of an additional antiretroviral drug on full viral suppression. Some authors used methodology enabling to concentrate the HIV-1 RNA by extracting from 4mL up to 30mL of plasma following ultracentrifugation [15-17], or repeat the test 3 times [18], lowering the detection limits of PCR and reducing the variability in the low copy number range. Those modified assays may be useful to answer scientific questions about low-level viraemia, but cannot be translated into clinical practice because the variability of most recent versions of widespread commercial VL assays is too high. "
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