Incidence and Determinants of Spontaneous Hepatitis B Surface Antigen Seroclearance: A Community-Based Follow-up Study

BACKGROUND & AIMS: Seroclearance of hepatitis B surface antigen (HBsAg) is one of the most important clinical outcomes for chronic hepatitis B treatment trials. Few studies have explored the incidence and determinants of spontaneous seroclearance using a long-term follow-up study. This study aimed to examine the natural history and predictors of HBsAg seroclearance. METHODS: A total of 3087 individuals with chronic hepatitis B virus infection were enrolled between 1991 and 1992 in this community-based study. Serum samples collected at baseline and follow-up examinations were tested for HBsAg, hepatitis B e antigen (HBeAg), serum hepatitis B virus (HBV)-DNA levels, and anti-hepatitis C virus serostatus. Cox proportional hazards models were used to estimate HBsAg seroclearance rate ratios associated with various determinants. RESULTS: HBsAg seroclearance occurred in 562 participants during 24,829 person-years of follow-up evaluation, giving a 2.26% annual seroclearance rate. HBV-DNA levels at baseline and follow-up evaluation were the most significant predictor of seroclearance. Higher HBV viral loads conferred lower HBsAg seroclearance rates (P < .001). A spontaneous decrease in follow-up HBV-DNA level (>= 3 log) was associated significantly with seroclearance, showing an adjusted odds ratio of 4.17 (95% confidence interval, 2.55-6.82). Among those with seroclearance, 95.8% had undetectable HBV-DNA levels before seroclearance. Cumulative incidence of HBsAg seroclearance at 60 and 100 months after serum HBV-DNA level decreased to undetectable was 25.8% and 51.3%, respectively. CONCLUSIONS: This study reveals determinants of HBsAg seroclearance, and suggests that a low viral load is an important factor affecting the natural seroclearance of HBsAg, indicating significant clinical implications for the treatment of chronic HBV.