BACKGROUND: Accurate detection of Hepatitis B Surface Antigen (HBsAg) is an important aid in the diagnosis of patients infected with the hepatitis B virus (HBV). A multi-center study was conducted to characterize the performance of the HBsAg assay on the family of Access immunoassay systems from Beckman Coulter.

METHODS: The Access HBsAg assay was characterized in a multi-center study and compared to the Abbott AxSYM* and PRISM* HBsAg assays. The bioMérieux VIDAS* assay was used to resolve discrepant results. Reproducibility studies (intra-assay, inter-assay and inter-lot) were performed with pooled serum samples (negative sample, close to cut off, low, medium and high positive samples). Analytical sensitivity, subtype and genotype detection were studied with various commercial panels (SFTS panel, WHO 80/549, WHO 00/588, Teragenix HBV Genotype panel). A panel of recombinant HBsAg mutant proteins was tested to investigate reactivity towards genetic mutations. Clinical sensitivity was verified with seroconversion panels and samples from subjects with known HBV infection. Analytical specificity was studied with samples from patients with potential cross-reactive infections. Clinical specificity was validated among blood donors and a hospitalized population.

RESULTS: The imprecision was < 10%. Analytical sensitivity was < or = 0.1 ng/mL (SFTS panel), 0.020 PEI Units/mL (ad panel), 0.024 PEI Units/mL (ay panel), 0.092 IU/mL with WHO 80/549 and 0.056 IU/mL with WHO 00/588. All genotype samples and HBsAg mutants were reactive with the Access HBsAg assay. Seroconversion panels tested showed no significant difference with the reference method. Sensitivity for subjects with known HBV infection was 100%. No interference with potentially cross-reactive infections was observed after confirmatory testing. Specificity was 99.96% (100% after confirmatory testing) in a blood donor population and 99.5% (100% after confirmatory testing) in a hospitalized population. Excellent separation of positive and negative populations was observed.

CONCLUSIONS: The Access HBsAg and HBsAg Confirmatory assays meet all clinical and analytical performance requirements of assays for the detection of HBsAg.