Performance of the cobas® HBV RNA automated investigational assay for the detection and quantification of circulating HBV RNA in chronic HBV patients.

Background: The amount of HBV RNA in peripheral blood may reflect HBV covalently closed circular DNA (cccDNA) transcriptional activity within infected hepatocytes. Quantification of circulating HBV RNA (cirB-RNA) is thus a promising biomarker for monitoring antiviral treatment.

Objectives: We evaluated the performance of an automated, prototype quantitative HBV RNA assay for use on the Roche cobas® 6800/8800 systems.

Study Design: The sensitivity, specificity, linearity, and potential interference by HBV DNA of the cobas® HBV RNA assay were assessed using synthetic HBV armored RNA and clinical specimens.

Results: cobas® HBV RNA results were linear between 10 and 10 copies/mL in clinical samples of several HBV genotypes, and up to 10 copies/mL with synthetic RNA. Precision and reproducibility were excellent, with standard deviation below 0.15 log copies/mL and coefficients of variation below 5% throughout the linear range. The presence of HBV DNA had minimal (<0.3 log copies/mL) impact on HBV RNA quantification at DNA:RNA ratios of up to approximately one million. In a panel of 36 untreated patient samples, cirB-RNA concentrations were approximately 200-fold lower than HBV DNA. cirB-RNA was detected in all 13 HBeAg-positive patients (mean 6.0 log copies/mL), and in 20 of 23 HBeAg-negative patients (mean of quantifiable samples 2.2 log copies/mL). Finally, cirB-RNA was detected in 12 of 20 nucleoside analog-treated patients (mean of quantifiable samples 3.4 log copies/mL).

Conclusions: The cobas® 6800/8800 investigational HBV RNA assay is a high throughput, sensitive and inclusive assay to evaluate the clinical relevance of cirB-RNA quantification in patients with chronic hepatitis B.