Abstract: An immunoassay for detecting disease associated Ig, such as IgM associated with acute forms of Toxoplasma gondii infection. Wells of microtiter plates are first coated with an antibody against the Ig to be detected and the test sample, e.g. serum, is then added and incubated. After removal of non-adsorbed materials from the wells, an insoluble visible form of the cognate antigen to the Ig, such as antigen fixed to latex particles, is added. If no such Ig is present in the sample, the antigen will appear as a smooth button on the bottom of the well; whereas if such Ig is present in significant quantity, the antigen will be captured by adsorbed antiIg-Ig complexes and distributed on the wall of the well according to the distribution of the antiIg-Ig complex thereon.