Hepatitis B surface antigen loss (HBsAg) is a primary therapeutic aim in the management of chronic hepatitis B (CHB), HBsAg levels may be a surrogate marker of infected cells in the liver, and is considered as the only possible
quantitative assay for intrahepatic viral load in treated patients with undetected viremia. A rapid HBsAg decline during nucleoside/nucleotide (NA) therapy may identify patients who will show clearance of HBsAg. Currently, there is no consensus on the clinical utility of serum HBsAg monitoring for evaluating patient responses to NA therapy. We aimed to evaluate the possible value of HBsAg quantitation for prediction of treatment response to oral antiviral therapy. This prospective study was carried out on 130 CHB patients treated with oral antiviral therapy in outpatient clinic of Internal Medicine Department, Mansoura University Hospital and Egyptian Liver Research Institute and Hospital during the period from March 2011 to March 2015. Eighty five patients were on Lamivudine, 27 patients were on Entecavir, 11 patients were on Tenofovir and 7 patients were on Adifovir. Patients were checked every 6 months after starting treatment for 3 years. Twelve out of 130 patients partially responded to the therapy, 9 cases were break through, 103 cases responded and 6 cases achieved HBsAg loss, the baseline HBsAg level has a high predictive value for HBsAg loss vs other patients (AUROC= 0.870, P < 0.01) at cutoff value ≤1927.50 IU/mL with a sensitivity of 83.3%, a specificity of 73.4%, a PPV of 83.15%, and an NPV of 98.9%. While cut off value of ≤128.50 after 6 months of treatment has a sensitivity of 83.3%, a
specificity of 98.4%, a PPV of 71.4%, and an NPV of 99.2%. Significant HBsAg decline to 128.5 IU/ml after starting treatment is useful predictor for patients that can achieve HBsAg loss.