Serum hepatitis B surface antigen (HBsAg) level < 100 IU/ml and undetectable hepatitis B virus (HBV) DNA have been recently proposed as an alternate endpoint of "partial cure" in chronic hepatitis B (CHB). We investigated clinical outcomes of hepatitis B e antigen (HBeAg)-negative CHB patients with HBsAg <100 IU/ml and undetectable HBV DNA. Treatment-naïve HBeAg-negative CHB patients with undetectable HBV DNA and normal alanine aminotransferase were retrospectively included from three institutions. Patients were classified into the low HBsAg group (<100 IU/ml) and the high HBsAg group (≥100 IU/ml). Liver fibrosis was evaluated by noninvasive tests (NITs). A total of 1218 patients were included and the median age was 41.5 years. Patients with low HBsAg were older (45.0 vs. 40.0 years, P < 0.001) than those in the high HBsAg group, while the NIT parameters were comparable between groups. During a median follow-up of 25.7 months, patients with low HBsAg achieved a higher HBsAg clearance rate (13.0% vs. 0%, P < 0.001) and a lower rate of significant fibrosis development (2.2% vs. 7.0%, P = 0.049) compared to patients with high HBsAg. No patient developed HCC in either group. HBsAg level was negatively associated with HBsAg clearance (HR 0.213, P < 0.001) and patients with HBsAg < 100 IU/ml had a low risk of significant fibrosis development (HR 0.010, P = 0.002). The optimal cutoff value of HBsAg for predicting HBsAg clearance was 1.1 Log10 IU/ml. Treatment-naïve HBeAg-negative CHB patients with HBsAg <100 IU/ml and undetectable HBV DNA had favourable outcomes with a high rate of HBsAg clearance and a low risk of fibrosis progression.
Keywords: Chronic hepatitis B; HBsAg clearance; hepatitis B surface antigen; liver fibrosis.