Flocculation test:

Flocculation is a form of agglutination in which the antigen is found in colloidal form instead of being particulate. In this flocculation test, the antigen - antibody complexes become aggregated in small floccules, which should be read microscopically using a low power objective at a total magnification of 100X. Probably the most useful example of flocculation test is the VDRL (VENEREAL DISEAE RESEARCH LABORATORY) test for syphilis. In this test an antigen is used which is not of microbial origin.