摘要Background and aim:Few studies have reported hepatitis B surface antigen(HBsAg)kinetics after nucleos(t)ide analog(NA)discontinuation in patients with noncirrhotic chronic hepatitis B(CHB).The study specifically investigated long-term HBsAg kinetics after NA discontinuation.Methods:Between January 2014 to January 2024,this study prospectively enrolled 106 outpatients with noncirrhotic CHB who met the discontinuation criteria after NA consolidation treatment.Demographic,clinical,and laboratory data were collected and analyzed after NA discontinuation.Results:Ninety-six patients who finished 5 years of follow-up were included.HBsAg remained unde-tectable in 29 patients with end of treatment(EOT)HBsAg negativity.Among 67 patients with EOT HBsAg positivity,HBsAg seroclearance occurred in 12(17.9％)patients with an estimated annual inci-dence of HBsAg seroclearance of 3.6％.Patients with EOT HBsAg levels of ≤1000 IU/mL had a higher HBsAg seroclearance rate than those with EOT HBsAg levels of＞1000 IU/mL(33.3％vs.5.4％).The pro-portion of patients with HBsAg ≤1000 IU/mL increased during follow-up.Logistic regression analysis indicated that the EOT HBsAg level was an independent factor for HBsAg seroclearance and an HBsAg level decline exceeding 1 log10 IU/mL.The optimal EOT HBsAg cutoff for both HBsAg seroclearance and an HBsAg level decline exceeding 1 log10 IU/mL was 359 IU/mL.Conclusions:Patients with EOT HBsAg negativity experienced no relapse and maintained HBsAg sero-clearance during 5 years of follow-up after NA discontinuation.A higher HBsAg seroclearance rate can be obtained in patients with EOT HBsAg levels of ≤1000 IU/mL during 5 years of follow-up after NA discontinuation.Close monitoring and proper NA retreatment are recommended to guarantee the safety of NA discontinuation.