serologic tests in which a known quantity of antigen is added to the serum prior to the addition of a red cell suspension. Reaction result is expressed as the smallest amount of antigen which causes complete inhibition of hemagglutination.
Hemagglutination and www.motifolio.com
Components of the HI Assay www.cdc.gov
Hemagglutination inhibition lookfordiagnosis.com
Figure: Haemagglutination test www.swine-influenza.com