Efficacy and safety of switching from entecavir to tenofovir for chronic hepatitis B patients with sustained viral supression: a randomized controlled trial

INTERVENTION: Tenofovir disoproxil fumarate 300mg/day daily treatment period: 3 yaers Entecavir 0.5mg/day daily treatment period: 3 yaers CONDITION: chronic hepatitis B PRIMARY OUTCOME: Number of patients who achieve the reduction of hepatitis surface antigen more than 0.5 log IU/mL for three years SECONDARY OUTCOME: 1) The rates of negativity of hepatitis B e antigen for three years; 2) The rates of negativity of hepatitis B surface antigen and achieving below 100 IU/mL or 1000 IU/mL of hepatitis B surface antigen levels for three years; Predictive factors of the reduction of hepatitis B surface antigen; 3) The rates of viral breakthrough for three years; 4) The chenges of serum creatinine and phosphate for three years INCLUSION CRITERIA: Patients treated with entecavir for more than one year Inclusion criteria as following; 1) Hepatits B surface antigen positive 2) HBV DNA levels < 3.0 log copies/mL for more than one year 3) Absence of renal impairment (serum creatinine levels <1.1mg/dL, eGFR >60 ml/min/1.73m2 and creatinine clearance >50ml/min) 4) Absence of hypophosphatemia (serum phosphate >2.8 mg/dL)