Conclusions: The virologic response within 4 weeks could be useful for prediction of ER and HBeAg seroconversion of adefovir therapy. Failing to EVR might not predict NR. Objectives: To determine the accuracy of HBcIgM in diagnosing AHB and the correlation between HBcIgM and liver inflammation (ALT), bilirubin & biosynthetic functions (albumin,PT). Result: A total of 233 patients were included: in 40 patients, ADV was added on LAM (add-on therapy), and in 193 patients, LAM was switched to ADV (switch therapy). During 16.5 months of follow-up, 25 patients developed ADV resistance (rtA181V and/or rtN236T) and all had undergone switch therapy. The cumulative probability of ADV resistance at the 24th month was 17.5%. Although add-on therapy induced no ADV resistance, it failed to show significant superiority over switch therapy (P=0.220). In multivariable analysis, female (odds ratio [OR], 2.75; 95% confidence interval [CI], 1.22-6.17; P=0.014), liver cirrhosis (OR, 2.39; 95% CI, 1.07-5.33; P=0.033), and age >45 yr (OR, 3.31; 95% CI, 1.14-9.66; P=0.028) were independent risk factors of ADV resistance.