An evaluation of tests in routine use for the quantitation of antibody to hepatitis B surface antigen

A quality control survey of various kits for measuring antibody to hepatitis B surface antigen (anti-HBs) was undertaken by the Serology Special Interest Group of the Australian Society of Microbiology due to concern about the performance of these tests in the field. A total of 20 panels of sera, derived from people with diverse histories with respect to hepatitis B infection and vaccination, were distributed to 19 participating laboratories using seven different commercial anti-HBs assays (representing five manufacturers) throughout Victoria. Participants were blinded with respect to replicates. Assay results were analysed to take account of the market dominance of the Abbott IMx method. In general, all tests performed adequately with respect to linearity over the range tested. Reproducibility within and between assays shows that some assays are performing inadequately in the field for quantitating anti-HBs. There was only one false positive result, from a laboratory using Amerlite, but a small number of results where a person's immune status would have been falsely reported as non-immune. Additionally, the two laboratories which used the same radioimmunoassay (RIA) test kit reported in different units, so that numerically values six to 12 times higher were reported by one laboratory compared to the other. These results underscore the need for statistically relevant independent evaluation in the absence of the licensing of kits prior to market release, and ongoing monitoring of test performance in the field, including participation in quality assurance exercises which should be regularly available.