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Updated: Jun 23, 2026
Amplifying and Quantifying HIV-1 RNA in HIV Infected Individuals with Viral Loads Below the Limit of Detection by Standard Clinical Assays
Published on: September 26, 2011
Quantitation of human immunodeficiency virus type 1 viral load in plasma using reverse transcriptase activity assay
Madisa Mine1, Keabetswe Bedi, Talkmore Maruta
1National Health Laboratory, 5353 Church Road, Extension 10, Gaborone, Botswana. mmine@bhp.org.bw
Insights
The Cavidi ExaVir Load v2 assay offers a reliable, cost-effective alternative for HIV viral load monitoring in Botswana. This study found it comparable to the gold standard COBAS Amplicor monitor v1.5, enabling decentralized testing.
Area of Science:
- Virology
- Clinical Diagnostics
- Public Health
Background:
- The Roche COBAS Amplicor monitor v1.5 assay is the gold standard for HIV viral load monitoring in Botswana.
- Its infrastructure requirements limit testing to national reference laboratories, hindering access in rural areas.
Purpose of the Study:
- To evaluate the Cavidi ExaVir Load v2 assay as a decentralized viral load testing alternative.
- To compare its performance against the COBAS Amplicor monitor v1.5 assay in a district hospital setting.
Main Methods:
- Performance comparison of ExaVir Load v2 and COBAS Amplicor monitor v1.5 assays.
- Utilized quality assessment samples and plasma from HIV-positive individuals.
- Statistical analysis included Kappa statistic and correlation coefficient.
Main Results:
- High agreement between ExaVir Load v2 and COBAS Amplicor monitor v1.5 assays (Kappa = 0.951).
- Strong correlation observed (r=0.8554, P<0.0001).
- ExaVir Load v2 detected HIV-1 RNA in 86 samples, COBAS in 84; concordant detection in 82 samples.
Conclusions:
- Cavidi ExaVir Load v2 assay is a simple, reliable, and adaptable alternative for decentralized viral load testing.
- It offers a lower cost per test compared to RT-PCR.
- ExaVir Load v2 systems have been implemented in multiple district and primary hospitals.
Abstract:
Roche COBAS Amplicor monitor version 1.5 assay is considered gold standard for viral load monitoring in Botswana. Due to its demand for elaborate infrastructure, viral load testing has been confined to the national HIV reference laboratories. Cavidi ExaVir Load version 2 assay was considered as a potential alternative to decentralize viral load testing to the rural/remote hospital laboratories and thus increase access to therapy. This study compared the performance of ExaVir Load v2 assay at a district hospital laboratory in Serowe and COBAS Amplicor monitor v1.5 assay at the Botswana Harvard HIV Reference Laboratory using quality assessment samples and plasma from HIV-positive individuals. ExaVir Load v2 and COBAS Amplicor monitor v1.5 assays had very good agreement; Kappa statistic 0.951. The COBAS Amplicor monitor v1.5 and ExaVir Load v2 assays detected HIV-1 RNA in 84 and 86 samples but did not detect HIV-1 RNA in 221 and 219 samples, respectively. The two assays detected HIV-1 RNA concordantly in 82 samples and were strongly correlated (r=0.8554, P<0.0001). ExaVir Load v2 assay provided a simple and reliable alternative viral load system that is adaptable to district hospital laboratories. The cost per test is less than RT-PCR. The ExaVir Load v2 systems have since been placed in four more district and primary hospital laboratories.
