Factors associated with the biphasic kinetics of serum HBV RNA in patients with HBeAg-positive chronic hepatitis B treated with nucleos(t)ide analogues.

Background: Serum hepatitis B virus (HBV) RNA is a novel biomarker for evaluating treatment response. Detailed information regarding serum HBV RNA kinetics during treatment with nucleos(t)ide analogues (NAs) is limited.

Aims: To ascertain serum HBV RNA kinetics during long-term NA treatment and identify associated factors.

Methods: We enrolled 76 HBeAg-positive chronic hepatitis B patients receiving NA from randomised controlled trials. Laboratory assays were undertaken every 3 months. Factors associated with serum HBV RNA kinetics were identified by generalised estimating equations.

Results: Baseline serum HBV RNA was 8.5 ± 1.0 log  copies/mL. Decline in serum HBV RNA during NA therapy was biphasic: the first phase (HBV DNA detectable) had a fast decrease (median slope, -0.207 log  copies/mL/month) and was followed by a second phase (HBV DNA undetectable) with slow decrease (median slope, -0.071 log  copies/mL/month). In the first phase, factors independently associated with lower initial serum HBV RNA were male sex (OR, 0.685, P = 0.044), low baseline HBsAg (OR, 0.525, P = 0.001) and rapid virological response (RVR) (OR, 0.624, P = 0.031). In the second phase, only RVR was independently associated with serum HBV RNA kinetics, including its lower initial level (OR, 0.694, P = 0.043) and greater decline (OR, 0.966, P = 0.002). Based on viral dynamics, time needed to achieve undetectable serum HBV RNA from baseline was 43.56 (IQR: 29.49-66.40) months.

Conclusion: RVR was a significant determinant for biphasic decline in serum HBV RNA during NA treatment, which significantly influenced the treatment duration required to achieve undetectable serum HBV RNA.