ABSTRACT
The clinical implication of the hepatitis B surface antigen (HBsAg) concentrations has been reported in HBV-infected patients during anti-viral treatment. HBV genotypes A and D are ubiquitous and scattered worldwide, especially northern America as well as Europe, whereas genotypes B and C are common in Asia. The aim of this study was to evaluate a new version of the Sysmex HBsAg quantitative kit based on Chemiluminescence Enzyme Immunoassay. Sera collected from 172 patients infected with any of the four major genotypes A to D (HBV/A, n = 18; B, n = 25; C, n = 84; D, n = 45), including the genotype D cases with weak reaction in the previous version of the kit. The new version of the kit having additional monoclonal antibody, showed improved sensitivity compared to the previous version as well as robust correlation with another quantitative HBsAg assay: the Abbot Architect. Observed during lamivudine therapy, increase in HBsAg and HBV DNA concentrations preceded the aminotransferase (ALT) elevation associated with drug-resistant HBV variant emergence (breakthrough hepatitis). In conclusion, reliability of the Sysmex HBsAg quantitative assay was confirmed for the four HBV genotypes common worldwide. Monitoring of serum HBsAg concentrations in addition to HBV DNA quantification, is helpful in evaluation of the response or resistance to anti-viral therapy.