Evaluation of 17 CE-marked HBsAg assays with respect to clinical sensitivity, analytical sensitivity, and hepatitis B virus mutant detection.

Seventeen HBsAg assays, in use in the European market (CE-marked), were assessed for their diagnostic sensitivity using 38 commercially available seroconversion panels, and for their analytical sensitivity with the HBsAg ad and ay standards of the Paul-Ehrlich-Institut (PEI). In addition, the ability to detect HBsAg mutants was investigated by means of 21 recombinant HBsAg mutant samples and 5 natural mutants. Analysis of seroconversion data revealed that there were marked differences in the sensitivity among the CE-marked HBsAg assays. Differences in the window period between the most and the least sensitive assays were up to 2 weeks. Analytical sensitivities of the investigated assays ranged from 0.009 to 0.05 PEI-U/ml for HBsAg ad standard (relating to approximately 0.018 to 0.100 IU/ml of the 2nd WHO HBsAg standard) and 0.012 to 0.11 PEI-U/ml for the ay standard. Clinical and analytical sensitivities were basically correlated. The capacity to detect mutant HBsAg forms was influenced by the assay format and the properties of the monoclonal antibodies used for coating of the solid phase or in the conjugate. While some assays detected all mutants others exhibited weaknesses especially in recognising HBsAg mutations affecting loop 2 of the HBsAg a-determinant. The results obtained with the recombinant mutants were largely confirmed by the investigation of clinical samples. The study gives a broad overview of the current state of the art of about 70% of the HBsAg assays currently available in Europe. The overall sensitivity has not been improved further since 1995 when the most sensitive assay was introduced into the market. In addition, detection of HBsAg mutants seems problematic with several assays. It is concluded that there is potential to improve clinical sensitivity and mutant recognition of HBsAg assays.