Evaluation of different radioimmunoassay methods for quantitative anti-HB determination

To contribute to the standardization of anti-HB determinations, five methods of quantitative anti-HB determination were compared: CEP dilution titration; RIA dilution titration; RIA unit determination; RIA parallel-line bioassay; and determination of binding capacity by quantitative immunoelectrophoresis. Anti-HB positive sera - the same five sera, in various dilutions, were subjected to the five tests. When comparing the overall results of the different titration methods, the following may be noted. The CEP method is very insensitive and yields relatively less favourable results with HBIG preparations. This is possibly related to the absence of adequately precipitating antibodies. There is no relationship between CEP and RIA dilutions titrations: HBIG (50 IU) is the least potent in CEP, most potent in RIA. But, of course, HBIG (50 IU) is standardized by a RIA method. The RIA dilution titration yields the same overall results as the two other RIA methods (RIA units and parallel-line bioassay), yet the dilution method is less accurate because of the way in which the titre is determined (= last dilution before cut-off). The RIA units determination and the parallel-line bioassay give somewhat similar results. There seems to be a nearly constant ratio between both these numerical results: RIA units/3000 approx.= IU/mL. In the parallel-line bioassay it seems that the results cannot be interpreted for antisera produced in another animal species. (author)