Rapid, random-access, and quantification of hepatitis B virus using the Cepheid Xpert HBV viral load assay

Abstract

Background: Monitoring viral load (VL) is an essential part of the management of patients chronically infected with hepatitis B virus (HBV). The commercial HBV VL assays currently available are generally performed on high-throughput platforms for batch wise testing of plasma samples, with relatively long turn-around-times. Rapid VL testing could provide immediate input to clinical decision making.

Methods: One hundred two stored plasma samples from 102 patients who were previously tested for HBV VL by the Cobas Ampliprep/Taqman or Cobas 4800 (Roche, Pleasanton, CA), were analyzed by the recently introduced Cepheid Xpert HBV Viral Load Assay. Thirty-one of the 102 samples were negative for HBV DNA and 71 out of 102 samples had a detectable VL. HBV DNA loads ranged from <20 to 5E8 IU/mL. HBV genotypes (A, B, C, D, E, and G) were known for 52 of the VL positive samples. Correlation of VL results between both assays was determined by the Pearson correlation coefficient (r² ). The level of concordance was assessed using the Bland-Altman analysis.

Results: HBV VLs correlated well between both assays, across all genotypes (Pearson correlation coefficient r² = 0.987). Six samples exceeded a 0.5 log difference between assays. Bland-Altman analysis demonstrated a mean of the difference of -0.107 log and a standard deviation of 0.271 log.

Conclusion: High correlation was observed between the Roche Cobas HBV Viral Load tests and the Xpert HBV Viral Load Assay, thus enabling rapid, random access, and accurate HBV VL assessment.

Keywords: hepatitis B virus; molecular diagnostics; random-access testing; viral load.

Figure 1

Correlation curve for the GeneXpert versus the Cobas ampliprep/taqman/4800

Figure 2

Bland‐Altman plot for Cobas ampliprep/taqman/4800 versus GeneXpert. The solid line marks the mean difference, while the dashed lines mark the limits of agreement