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 7 copies/mL in clinical samples of several HBV genotypes, and up to 10 9 copies/mL with synthetic RNA. Precision and reproducibility were excellent, with standard deviation below 0.15 log 10 copies/mL and coefficients of variation below 5% throughout the linear range. The presence of HBV DNA had minimal (<0.3 log 10 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 10 copies/mL), and in 20 of 23 HBeAg-negative patients (mean of quantifiable samples 2.2 log 10 copies/mL). Finally, cirB-RNA was detected in 12 of 20 nucleoside analog-treated patients (mean of quantifiable samples 3.4 log 10 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.