The detection of HBsAg mutants expressed in vitro using two different quantitative HBsAg assays

Abstract Background The quantification of hepatitis-B surface antigen (HBsAg) is useful to identify inactive carriers in chronically HBV infected patients and to predict interferon treatment outcome. Objective To compare two quantitative HBsAg assays for the detection of HBsAg mutants expressed in vitro. Study design HBsAg mutants ( n = 35) were expressed in HuH7 cells and the supernatants were tested in two different quantitative HBsAg assays (Architect, Abbott and Elecsys, Roche). Results All HBsAg mutants were detected by both assays, but in general the results of the Architect system were higher than those of the Elecsys system. The detection of HBsAg mutants in comparison to wild type was similar using both assays. However, HBsAg mutation T123A was under quantified by the Architect, whereas HBsAg mutations P142L, P142S and G145K yielded lower results in the Elecsys system. Conclusions Even though HBsAg assays are optimised for the detection of HBsAg mutants, discrepant results were obtained for some HBsAg mutants in two quantitative HBsAg assays. These findings have to be considered when testing samples from one patient with two different quantitative HBsAg assays.