A WHO reference reagent to standardize haemagglutination testing for anti-A and anti-B in serum and plasma: international collaborative study to evaluate a candidate preparation.

ABSTRACT

BACKGROUND AND OBJECTIVES: The aim of the study was to evaluate a lyophilized serum preparation, 14/300, for its suitability to serve as a World Health Organization (WHO) Reference Reagent to standardize and control haemagglutination titrations for anti-A and anti-B in serum and plasma, in an international collaborative study. MATERIALS AND METHODS: Serum preparation 14/300 and two plasma-based reserve preparations, 14/304 (high titre anti-A) and 14/208 (high titre anti-B), were titrated by 24 laboratories in 13 countries using direct (DRT) and indirect (IAT) haemagglutination techniques. RESULTS: There was eightfold to 64-fold variation in reported titres per preparation and method across laboratories, that is, titres extended over 4-7 dilutions, although intralaboratory variability was generally good, with over 90% of replicate titres within a twofold range. There was a reduction in interlaboratory variability when titres of the reserve preparations were adjusted relative to those of the candidate Reference Reagent. CONCLUSION: The establishment of 14/300 as a WHO Reference Reagent for high titre anti-A and anti-B in serum, with nominal anti-A and anti-B titres of 128 for DRT, and nominal anti-A and anti-B titres of 256 for IAT, will facilitate global standardization of haemagglutination titrations for anti-A and anti-B in patient samples and blood components.