∞ generated and posted on 2016.03.20 ∞
Adherence of antigens to particles that is followed by determination of ability of antibodies to clump those particles together.
The indirect agglutination test is described as indirect because the material that is being agglutinated is not the inherent carrier of the antigen but instead an artificial one. This test is also described as a passive agglutination test. See by contrast the direct agglutination test in which cells are employed for agglutination rather than artificial particles.
Though bentonite clay can be used as particles for the indirect agglutination test, in more modern times it has been more common to employ synthetic carriers, i.e., beads. In the latex agglutination test, a.k.a., latex fixation test, those beads consist, of course, of latex.
Note that it is also possible to coat particles or beads with antibodies, which can then become clumped together via the application of antigen to which the particle-affixed antibodies then bind. This approach results in agglutination, however, only if the supplied antigen possesses a valence of greater than one such that the necessary crosslinking between beads can occur.