A competitive enzyme-linked immunoassay using erythrocytes fixed to microtitre plates for anti-D quantitation in immunoglobulin products

Background and Objectives: The batch control of anti-D immunoglobulin for p revention of haemolytic disease of the newborn necessitates assessment of i ts potency. Anti-D quantitation is usually performed using automated haemag glutination methodology although this can only be carried out in specialist centres, The aim of this study was to develop a simple and robust assay fo r anti-D quantitation, Methods: We developed a competitive enzyme-linked im munoassay (EIA) in which unlabelled anti-D immunoglobulin and a biotinylate d monoclonal anti-D compete for red cell binding. Binding of biotinylated a nti-D is detected using an alkaline-phosphatase-labelled avidin preparation . The assay is conveniently carried out using erythrocytes fixed to microti tre plates. Results: The competitive EIA was specific for anti-D activity, highly reproducible and showed good correlation with manufacturers' potency estimates using automated haemagglutination, The assay was quick and simpl e to perform using freshly prepared or stored plates, and the biotinylated monoclonal anti-D could be lyophilized in ampoules for distribution as a st andardized reagent. Conclusions: The competitive EIA described can be used for the specific quantitation of anti-D and provides a robust alternative m ethod to automated haemagglutination, Copyright (C) 2000 S. Karger AG, Base l.