Serum hepatitis B surface antigen (HBsAg) kinetics in hepatitis B e antigen (HBeAg)-negative chronic hepatitis B

BACKGROUND: We investigated the differences in HBsAg kinetics at different levels of viremia in hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (CHB). METHODS: We compared HBsAg levels among HBeAg-negative CHB patients with persistently undetectable HBV DNA (≤20 IU/mL; Group A, n = 100), HBV DNA 20–2,000 IU/mL (Group B, n = 100), and HBV DNA >2,000 IU/mL (Group C, n = 100). HBsAg and HBV DNA levels were measured at three consecutive time points during follow-up (median 21.4 months). RESULTS: Median HBsAg levels were significantly lower in Group A than in Groups B and C at all time points (p < 0.001). HBV DNA and HBsAg levels were weakly correlated (r = 0.180 and 0.151 for Groups B and C, respectively). Among patients with HBsAg <100 IU/mL, Group A patients had the greatest median serum HBsAg reduction (0.341 log IU/mL/year; Group B, 0.122 log IU/mL/year; Group C, 0.057 log IU/mL/year; p = 0.002). Among Group A patients with HBsAg <100 IU/mL, baseline HBsAg achieved an AUROC of 0.876 in predicting >1 log annual HBsAg reduction; 10–100 IU/mL HBsAg was the optimal level for prediction (sensitivity 90 %; specificity 74.6 %). Serum HBsAg/HBV DNA ratios were significantly higher in Group B than in Groups A and C (p < 0.05). CONCLUSIONS: HBV DNA and HBsAg were weakly correlated. Only patients with undetectable HBV DNA showed decline in HBsAg levels during follow-up. The greatest reduction in HBsAg levels occurred in patients with baseline HBsAg <100 IU/mL.