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Medical Definition of Haemagglutination inhibition
1. A variation of the haemagglutination technique. Some viral antigens, when coated on erythrocytes, spontaneously cause agglutination in the absence of antibody. In these situations, the specific antigen-antibody reaction actually prevents the agglutination of reagent RBCs. Haemagglutination inhibition cannot differentiate between isotypes of specific antibodies (IgG, IgA or IgM) although positive haemagglutination inhibition analysis of specimens treated with Staphylococcus aureus Protein A (discussed above under coagglutination) to remove the IgG isotype antibodies has been used to imply the presence of specific IgM antibodies to the specific viral antigen. The crude quantitation of the specific antibodies is possible using serial dilution (titre). (05 Mar 2000)