A multi-center study comparing the analytical sensitivity and clinical concordance of three HIV-1 viral load assays

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.