Clinical usefulness of a novel high-sensitivity hepatitis B core-related antigen assay to determine the initiation of treatment for HBV reactivation

Backgrounds A fully automated, novel, high-sensitivity hepatitis B core-related antigen assay (iTACT-HBcrAg) has been developing. The purpose of this study is to evaluate the efficacy of measuring HBcrAg, using that assay, to diagnose HBV reactivation in a multi-center setting, compared with ultra-high-sensitivity HBsAg (iTACT-HBsAg) and HBV DNA assays. Methods Forty-four patients with HBV reactivation from 2008 to 2020 were enrolled in four hospitals. Serial serum specimens from the patients were assessed retrospectively for their HBcrAg levels by iTACT-HBcrAg (lower limit of detection; 2.0 log U/mL) and HBsAg levels by iTACT-HBsAg (lower limit of detection; 0.0005 IU/mL); these were compared to the HBV DNA levels. HBV reactivation was defined as detection of serum HBV DNA, including unquantifiable detection. Results At HBV reactivation and/or thereafter, HBV DNA levels were quantified (≥ 1.3 log IU/mL) in the sera of 27 patients, and were below the level of quantification (