Study of discrepancies in rubella haemagglutinin titrations and a reappraisal of diluents used in the rubella haemagglutination inhibition technique.

To elucidate inconsistencies in rubella haemagglutinin assays the components of the assay technique were examined. The results of carefully controlled assays of rubella haemagglutinin antigens from different sources in various plates and diluents with four species of indicator cells are reported. The quality and quantity of gelatin in the dextrose-gelatin-veronal buffered diluent commonly used in rubella haemagglutinin assays had a profound effect on the haemagglutination pattern and antigen titre. The veronal buffered saline used in the complement fixation test offered a valid alternative to the more complex diluents incorporating gelatin currently used in rubella haemagglutinin assays and haemagglutination inhibition tests.