Repeated Measurements of Hepatitis B Surface Antigen Identify Carriers of Inactive HBV During Long-term Follow-up

Background & Aims Measurements of hepatitis B surface antigen (HBsAg) and hepatitis B virus (HBV) DNA might help to identify carriers of inactive HBV. We assessed the performance of repeated measurements of HBsAg over a median time period of 8 years. Methods We performed a retrospective study of 292 HBe antigen–negative patients with chronic HBV infection, normal levels of alanine aminotransferase (ALT), levels of HBV DNA <20,000 IU/mL, and no cirrhosis who visited the outpatient clinics at 8 tertiary care centers in Europe, Asia, and Australia from 1990 through 2011. Patients were determined to be carriers of inactive HBV (level of HBV DNA <2000 IU/mL and serum levels of ALT that remained normal) or to have HBV activity (level of HBV DNA fluctuating >2000 IU/mL and/or abnormal levels of ALT) after each year of follow-up. Patients were followed for a median time of 8 years (range, 4–9 years). Dynamic regression analysis was used to study changes in level of HBsAg and HBV phase and to update the risk of HBV activity. Results One year after study enrollment, 189 patients (65%) had inactive HBV and 103 patients (35%) had HBV activity. Based on dynamic analysis, the probability that a patient would have HBV at any following year differed according to level of HBsAg; odds were 97% for patients with initial level of HBsAg <100 IU/mL, 85% for patients with initial levels 100–1000 IU/mL, and 76% for patients with initial levels >1000 IU/mL (P < .001). Having inactive virus for any 2 consecutive years predicted having inactive virus in any third year. However, 15% of patients with level of HBsAg >100 IU/mL had HBV activity in the third year. The combination of HBsAg level <100 IU/mL and HBV DNA level <2000 IU/mL identified patients whose virus remained inactive for the entire follow-up period, with 98% specificity and a positive predictive value of 97%, for all HBV genotypes. Patients with HBV activity who had levels of HBV DNA <5000 IU/mL and decreases in HBsAg of 0.5 log IU/mL or more for 1 year had a high probability of becoming carriers of inactive HBV in the next year. Conclusions In a retrospective, dynamic analysis of almost 300 patients with chronic HBV infection, we found that levels of HBsAg <100 IU/mL identify patients with inactive virus with a high level of specificity. HBsAg levels should therefore be used to define phases of HBV infection in HBe antigen–negative patients.

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