Evaluation of different calculation methods for anti-HBs titration.

Anti-HBs titre calculations should be standardized to make comparison between various vaccination programmes and between immunogenicity tests in animals more meaningful. For this purpose, we compared four methods of titre calculation in human and animal sera and in the IgM and IgG fractions of these sera. The four calculation methods are parallel line bioassay, Hollinger method, RIA units and regression-calibration curve. From our results, the following can be concluded: The titration curves of anti-HBs/IgM, anti-HBs/IgG and of animal sera do not always run parallel to the WHO standard curve. Thus, the objective quantification of these anti-HBs cannot be obtained with the WHO standard. The Hollinger method and the RIA units method are identical within the range S/P less than 1. They only differ by a factor of 4. Only dilutions giving results in the linear part of the dose-response curve should be considered for titre calculations. The mean of the results for different dilutions should be used to determine the titre. Within the restrictions mentioned, comparable results were obtained with the four methods.