Serum hepatitis B core-related antigen is an effective tool to categorize patients with HBeAg-negative chronic hepatitis B.

The discrimination between active chronic hepatitis B (CHB) and the clinically quiescent infection (CIB) is not always easy, as a significant portion of patients falls in a "grey" zone. Hepatitis B core-related antigen (HBcrAg) is a now quantifiable serological marker with potential applications in diagnosis and therapy monitoring. The aim of the present study was to evaluate the HBcrAg serum levels in HBeAg-negative HBV infection, and its ability in identifying the clinical profile, in comparison with HBsAg serum levels. HBcrAg was retrospectively assessed on serum samples from a population of treatment-naive HBeAg-negative patients by ChemiLuminescent Enzyme Immunoassay (CLEIA). HBsAg and HBV-DNA data were collected. Serological data were associated to clinical profile, defined in the subsequent follow-up of at least 1 year. In the overall population of 160 HBeAg-negative patients, HBcrAg results weakly correlated with qHBsAg levels (Spearman r = 0.471, P < 0.0001) and correlated closely with HBV-DNA (Spearman r = 0.746, P < 0.0001). HBcrAg levels were significantly higher in 85 CHB patients relative to 75 CIB carriers. A value of 2.5 logU/mL produced the optimal cut-off to identify CIB patients, with diagnostic accuracy comparable to HBsAg levels. In long-term clinical evaluation, a single measurement of HBcrAg at the established cut-off was optimally consistent with clinical outcome. Conversely, the HBsAg cut-off performed well in the true quiescent phase and less in more difficult-to-categorize patients. In conclusion, single-point use of HBcrAg serum levels provides an accurate identification of CIB and represents a useful tool for patient classification.