A prospective evaluation of Cepheid Xpert® and Roche cobas® HIV-1, HBV and HCV assays for nucleic acid quantification

Quantification of HBV DNA, HIV and HCV RNA allows monitoring of disease progression and management. An easy-to-use cartridge-based real-time polymerase chain reaction (PCR) assay for quantification of HIV, HBV and HCV can provide supplementary benefits, for example, in low resource settings instead of large, automated PCR systems. Our aim was to assess interassay agreement between Cepheid Xpert HIV-1 Viral Load XC, HBV Viral Load and HCV Viral Load, and Roche cobas HIV-1, HBV and HCV assays with routine patient samples analyzed prospectively with both GeneXpert and cobas 6800 PCR systems.

EDTA plasma (HIV-1) or serum (HBV and HCV) samples were used to evaluate agreement of quantitative viral load analyzed with GeneXpert and cobas 6800 PCR systems. Interassay agreement was evaluated with Bland-Altman method and concordance correlation coefficient.

Of 263 clinical samples, 135 (51%) were available for quantitative comparison. Viral load was 0.081 log₁₀ cp/ml lower for HIV-1 (n = 45), 0.197 log₁₀ IU/ml higher for HBV (n = 51) and 0.154 log₁₀ IU/ml lower for HCV (n = 39) with Xpert Viral Load assays compared to cobas assays. A large majority of samples (130/135, 96%) were within 95% limits of agreement. Concordance correlation coefficients varied from 0.985 to 0.991.

Our study confirms interchangeable results between Xpert HIV-1 Viral Load XC, HBV Viral Load and HCV Viral Load and the cobas HIV-1, HBV and HCV assays for quantitative comparisons and supports the use of Xpert assays as an alternative platform for viral load testing in appropriate clinical and laboratory settings.