An antibody adsorbed onto red cells, either in vivo or in vitro, can be dissociated and recovered through elution. The eluate can then be used to identify a single antibody in multispecific sera, demonstrate the presence of a weak antigen, identify the antibody responsible for a positive direct antiglobulin test in acquired haemolytic anaemia or transfusion reaction, identify the antibodies causing haemolytic disease of the newborn or prepare specific antibody from sera containing unwanted antibodies.