qHBsAg levels have been used to predict response to interferon (IFN) therapy in patients with chronic hepatitis B (CHB) primary treatment, but rarely in studies of nucleoside (acid) analog (NA) treated patients. At this year’s EASL annual meeting, the NEW SWITCH study led by Prof. Ren Hong from the Department of Infectious Diseases of the Second Hospital of Chongqing Medical University had the latest analysis showing that in HBeAg-positive patients who switched to pegylated interferon (PEG-IFN-α2a) treatment after a partial response with NA therapy, the combination of qHBsAg at baseline and at week 24 levels at baseline and week 24, predicted HBsAg clearance at week 48. The multicenter study included HBeAg-positive CHB patients treated with NA for 1 to 3 years who achieved a partial response (defined as HBV DNA <200 IU/mL and HBeAg clearance) and were randomized in a 1:1 ratio to switch to PEG-IFN-α2a treatment for 48 or 96 weeks, with overlapping NA treatment for the first 12 weeks and follow-up until discontinuation of PEG-IFN-α2a treatment. IFN-α2a treatment for 48 weeks after. In a retrospective analysis, the value of qHBsAg levels at baseline and at 12 and 24 weeks of treatment for predicting treatment response (defined as HBsAg clearance at week 48) was analyzed. A total of 271 patients who completed 48 weeks of treatment were included in the study, including 47 patients (17.3%) who achieved HBsAg clearance at week 48. Patients who achieved HBsAg clearance had significantly lower qHBsAg levels at baseline and more significant reductions in qHBsAg levels during treatment compared with patients who did not achieve HBsAg clearance (all P values <0.001). Patients with qHBsAg <1500 IU/mL at baseline achieved higher HBsAg clearance than those with qHBsAg ≥1500 IU/mL (33.3% vs. 4.1%, P<0.0001); similarly, patients with qHBsAg levels <200 IU/mL at week 24 achieved higher HBsAg clearance was higher in patients with qHBsAg levels <200 IU/mL at week 24 than in those with qHBsAg ≥200 IU/mL (48.4% vs. 0.6%, P<0.0001). < span=""> Analysis of the predictive value of the combined application of baseline and on-treatment qHBsAg levels showed that patients with qHBsAg <1500 IU/mL at baseline and qHBsAg <200 IU/mL at week 24 had the highest response rate (PPV: 51.35%), whereas those with qHBsAg ≥1500 IU/mL at baseline and The response rate was lowest in patients with qHBsAg ≥200 IU/mL at baseline (NPV: 100%).