Association of Hepatitis B Core-Related Antigen With Hepatitis B Virus Reactivation in Occult Viral Carriers Undergoing High-Risk Immunosuppressive Therapy.

OBJECTIVES: Hepatitis B core-related antigen (HBcrAg) is a novel serum marker that correlates with intrahepatic hepatitis B virus (HBV) activity. Its association with HBV reactivation in hepatitis B surface antigen (HBsAg)-negative antibody to hepatitis B core antigen (anti-HBc)-positive patients undergoing high-risk immunosuppressive therapy is undefined. METHODS: HBcrAg was measured in HBsAg-negative, anti-HBc-positive Asian patients with undetectable HBV DNA, who participated in two prospective studies investigating HBV reactivation during rituximab-containing chemotherapy and allogeneic hematopoietic stem cell transplantation (HSCT). Patients were monitored every 4 weeks for up to 2 years, with entecavir started when HBV reactivation, defined as HBV DNA ≥10 IU ml-1, developed. RESULTS: One hundred and twenty-four HBsAg-negative, anti-HBc-positive patients (rituximab, N=62; allogeneic HSCT, N=62) with a median follow-up of 64 weeks (range: 4-104 weeks) were studied. HBV reactivation occurred in 31 patients, with a 2-year cumulative reactivation rate of 40.4%. Serum HBcrAg was detected in 43 (34.7%) patients. Baseline HBcrAg positivity was significantly associated with HBV reactivation (P=0.004, hazard ratio (HR): 2.94, 95% confidence interval (95% CI): 1.43-6.07). HBcrAg-positive patients had a significantly higher 2-year HBV reactivation rate than HBcrAg-negative patients (71.8 vs. 31%, P=0.002). In the rituximab cohort, the HRs for positive HBcrAg and negative antibody to HBsAg for HBV reactivation were 3.65 and 2.84, respectively (P=0.011, 95% CI: 1.35-9.86 and P=0.032, 95% CI: 1.10-7.37, respectively). CONCLUSIONS: Serum HBcrAg positivity is a significant risk factor of HBV reactivation in HBsAg-negative, anti-HBc-positive patients undergoing high-risk immunosuppressive therapy and can potentially have a role in identifying patients who will best benefit from prophylactic nucleoside analogue treatment.