20.3 Agglutination assays  (Page 6/12)

[link] summarizes the various kinds of agglutination assays discussed in this section.

Key concepts and summary

• Antibodies can agglutinate cells or large particles into a visible matrix. Agglutination tests are often done on cards or in microtiter plates that allow multiple reactions to take place side by side using small volumes of reagents.
• Using antisera against certain proteins allows identification of serovars within species of bacteria.
• Detecting antibodies against a pathogen can be a powerful tool for diagnosing disease, but there is a period of time before patients go through seroconversion and the level of antibodies becomes detectable.
• Agglutination of latex beads in indirect agglutination assays can be used to detect the presence of specific antigens or specific antibodies in patient serum.
• The presence of some antibacterial and antiviral antibodies can be confirmed by the use of the direct Coombs’ test , which uses Coombs’ reagent to cross-link antibodies bound to red blood cells and facilitate hemagglutination .
• Some viruses and bacteria will bind and agglutinate red blood cells; this interaction is the basis of the direct hemagglutination assay , most often used to determine the titer of virus in solution.
• Neutralization assays quantify the level of virus-specific antibody by measuring the decrease in hemagglutination observed after mixing patient serum with a standardized amount of virus.
• Hemagglutination assays are also used to screen and cross-match donor and recipient blood to ensure that the transfusion recipient does not have antibodies to antigens in the donated blood.

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