Performance Evaluation of Cobas® HIV-1, a Quantitative Nucleic Acid Test for Use on the Cobas® 6800/8800 Systems

Background and objectives: HIV viral load testing is recommended for all patients on antiretroviral treatment. As viral load testing continues to scale up worldwide, highly sensitive and specific HIV viral load tests that support high throughput testing are needed to provide timely and accurate results. We evaluated the performance characteristics of the new cobas® HIV-1 test for use with the cobas® 6800/8800 system (cobas® HIV-1), and also assessed clinical correlation with the reference standard cobas®AmpliPrep/cobas®TaqMan® HIV-1 Test, version 2.0 (TaqMan®HIV-1 v2.0). Methods: The limit of detection (LoD), linearity, precision, analytical specificity, diagnostic sensitivity, and specificity of the cobas® HIV-1 test were evaluated. The method comparison to the TaqMan®HIV-1 v2.0 was assessed using Deming regression and Bland-Altman plot analysis, and the mean of the paired viral load difference between the two tests was also calculated using a paired t-test. Results: The cobas® HIV-1 test demonstrated an LoD of 13.2 copies/mL for HIV-1 M subtype B and a similar LoD for all other HIV-1 subtypes with a linear range of 13 to 1.73 × 107 copies/mL. The assay precision was high with a pooled SD of 0.05 to 0.12 log10 across the linear range. Diagnostic sensitivity using clinical samples was 99.25%, with a specificity of 100%. cobas® HIV-1 demonstrated excellent correlation to TaqMan®HIV-1 v2.0 (R2 =0.98). The overall percentage agreement between the two tests was also high (>95%) with a cutoff of 50 and 200 copies/mL. Conclusions: The cobas® HIV-1 test is a highly sensitive and specific method for viral load monitoring that has an improved limit of detection, lower sample volume, and increased throughput capability compared to TaqMan®HIV-1 v2.0. The novel cobas® HIV test has excellent correlation with the FDA-approved TaqMan® HIV-1 v2.0 test.