Use of hepatitis B virus core-related antigen to evaluate natural history of chronic hepatitis B

Background and Aim Hepatitis B core-related antigen (HBcrAg) has been shown to correlate with various viral markers in chronic hepatitis B, but its role in defining natural history is not well studied. We aimed to investigate the use of HBcrAg to define different phases of chronic hepatitis B. Methods Stored residual serum samples from longitudinal cohorts of chronic hepatitis B patients in Hong Kong and Japan were studied. Viral markers were measured in three serial serum samples for each patient. Patients were divided into six groups for analysis: hepatitis B e antigen (HBeAg)-positive chronic infection (EPI), HBeAg-positive chronic hepatitis (EPH), HBeAg seroconversion (ES), HBeAg-negative chronic hepatitis (ENH), HBeAg-negative chronic infection (ENI), and HBsAg seroclearance (SS). Results In total, 166 patients followed up for 100 (76-113) months were included. HBcrAg was correlated with hepatitis B virus DNA and HBsAg levels in both HBeAg-positive and HBeAg-negative patients. HBcrAg cut-off of >= 6.0 log U/mL could best differentiate HBeAg-positive from HBeAg-negative patients (area under receiver operating characteristic curve of 0.99, P < 0.001). HBcrAg could not differentiate patients in EPI and EPH phases, but HBcrAg declined dramatically at HBeAg seroconversion. In HBeAg-negative patients, HBcrAg >= 4.0 log U/mL could best differentiate ENH from ENI (area under receiver operating characteristic curve of 0.81; P < 0.001), with high specificity (81.6%) but only moderate sensitivity (65.7%) at baseline. Undetectable HBcrAg was found in 17%, 63%, and 89% patients in ENH, ENI, and SS groups at the last visit, respectively. Conclusions HBcrAg provides useful information to stage the natural history of chronic hepatitis B, particularly identifying HBeAg-positive patients and HBeAg-negative patients with active disease.