Performance of the Xpert HBV Viral Load assay versus the Aptima Quant assay for quantifying hepatitis B virus DNA

Quantification of HBV DNA is used for initiating and monitoring antiviral treatment. We have evaluated the Xpert HBV Viral Load (VL) assay on the GeneXpert instrument. We estimated its limit of detection to be 7.5 IU/mL. Reproducibility was 1.1-12.7% as assessed by the coefficients of variation for 3 different samples. The assay was linear from 2 to 8 log₁₀ IU/mL for HBV genotypes A to F. Its clinical performance was evaluated by testing prospectively 100 HBV DNA-positive samples with the Xpert HBV VL and Aptima Quant HBV assays. The results from the 2 assays were correlated, with a modest bias (-0.10 log₁₀ IU/mL) between them by Bland-Altman analysis. Patient monitoring with 80 samples performed with both assays gave similar patient profiles with trends in the same direction. The Xpert HBV Viral load assay is reliable enough for quantifying HBV DNA in clinical practice.