Direct Agglutination Test

∞ generated and posted on 2016.03.20 ∞

Detection of the presence of specific antibodies via their ability to clump cells.

Direct agglutination tests take advantage of the presence of antigens on the surface of cells – including those of pathogens or body cells (such as red blood cells – to determine not just the presence of antibodies of a given specificity but also their titer.

This assay is used in the testing for brucellosis, in distinguishing among serovars of Salmonella, and in testing for visceral leishmaniasis. When used diagnostically, a rise in titer is indicative of current exposure to a pathogen whereas a rise from zero is indicative of seroconversion.

Note that since cells will possess multiple antigens on their surface, the direct agglutination test as mediated by polyclonal serum can detect antibodies that are specific for multiple antigens simultaneously.