Abstract: A particle agglutination assay for antigens, antibodies and other binding proteins such as rheumatoid factor, uses two different, microscopic or submicroscopic particulate reagents. The first particulate reagent binds with the antigen or antibody under assay, and then the second particulate reagent is added which binds only to those first reagent particles which have bound to the antigen or antibody under assay, so causing agglutination. The free unbound first or second particles are assayed to indicate the presence and/or amount of the antigen or antibody under assay. The assay of rheumatoid factor may be so conducted to reveal the fractions of each immunoglobulin class of RF present. The assay is particularly useful for small quantities of antibodies present in human sera indicating allergy, infection or autoimmune diseases.

Abstract: The presence of antibodies (Ab) and antigens (Ag) in a liquid is detected by mixing the liquid with two different particulate reagents which mutually agglutinate but whose agglutination is inhibited by the particular Ab or Ag under assay. By detecting the extent of agglutination, the presence or absence of the Ab or Ag can be confirmed. By measuring the extent of agglutination or non-agglutination quantitatively, an amount of Ab or Ag can be determined. The particulate reagents preferably comprise latex.