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Updated: Oct 12, 2025
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
A multi-center study comparing the analytical sensitivity and clinical concordance of three HIV-1 viral load assays
Sergio Carmona1, Lucia Hans1, Merlin Njoya2
1HIV & Haematology Molecular Laboratory, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand - NHLS, Charlotte Maxeke Johannesburg Academic Hospital, Johannesburg, South Africa.
Insights
This study assessed the accuracy and concordance of three HIV-1 viral load assays. The cobas HIV-1 assay demonstrated high sensitivity and accuracy, making it suitable for clinical use in managing HIV-1.
Area of Science:
- Virology
- Clinical Diagnostics
- Molecular Biology
Background:
- HIV-1 viral load assays are critical for managing patients with HIV-1.
- Accurate quantification of HIV-1 RNA is essential for treatment monitoring and clinical decision-making.
Purpose of the Study:
- To evaluate the concordance between three distinct HIV-1 viral load assays.
- To assess the analytical sensitivity, precision, and accuracy of these assays.
Main Methods:
- Concordance was evaluated for three assays: cobas HIV-1, COBAS TaqMan HIV-1 Test v2.0, and COBAS AmpliPrep/COBAS TaqMan HIV-1 test v2.0.
- Analytical performance was assessed using the WHO 2nd International Standard for HIV-1.
- Accuracy and concordance were determined using 212 clinical specimens, with overall percent agreement (OPA) calculated at different viral load thresholds.
Main Results:
- All assays exhibited a limit of detection below 20 copies/mL.
- 100% hit rate was observed for concentrations ≥ 50 copies/mL, with cobas HIV-1 uniquely providing quantifiable data at this level.
- High concordance was found between assays, with OPA ranging from 94.8% to 99.0% across different thresholds (50, 200, and 1000 copies/mL).
Conclusions:
- The cobas HIV-1 assay demonstrates high sensitivity and accuracy.
- The assay is well-suited for routine clinical practice in HIV-1 management.
- The evaluated assays show strong agreement, supporting their use in clinical settings.
Background:
HIV-1 viral load assays are essential tools for clinical management of people living with HIV-1.
Objectives And Study Design:
We evaluated concordance between three assays: the cobas® HIV-1 test for use on the cobas® 6800 and cobas® 8800 systems (cobas HIV-1); the COBAS® TaqMan® HIV-1 Test, v2.0 for use with the High Pure System and the COBAS® AmpliPrep/COBAS® TaqMan® HIV-1 test, v2.0. Analytical sensitivity, precision and accuracy of all three methods were assessed using the WHO 2nd International Standard for HIV-1, with concentrations from 5 to 1000 copies/mL. Accuracy and concordance were evaluated using 212 clinical specimens. Overall percent agreement (OPA) was determined using three different thresholds used as medical decision points.
Results:
The limit of detection was below 20 copies/mL for each assay. The hit rate for each assay was 100 % for concentrations ≥ 50 copies/mL. Only the cobas HIV-1 test generated quantifiable data for all replicates at 50 copies/mL. Between 50 and 400 copies/mL, results for all assays were accurate within 0.09 log10 copies/mL, with standard deviation less than 0.14 log10 copies/mL. The mean difference between paired results in clinical specimens ranged from -0.050 to 0.107 log10 copies/mL across all assay comparisons. The OPA between pairs of assays ranged from 94.8 to 98.1% at the 50 copies/mL cutoff, and improved to a range of 97.6-99.0% at the 200 copies/mL cutoff. At the 1000 copies/mL cutoff, OPA between assays was 98.5-99.0%.
Conclusions:
The cobas HIV-1 assay is highly sensitive, accurate and suitable for use in clinical practice.
