Agglutination Reactions are similar in principle to precipitation reactions in that they depend on the crosslinking of polyvalent antigens.
Hemagglutination is used in blood typing. RBCs are mixed on a slide with antisera to the A or B blood group antigens. If the antigen is present on the cells, they agglutinate, forming a visible lump on the slide.
Bacterial agglutination is also used to diagnose infection. Serum from a patient is serially diluted in an array of tubes to which the bacteria is added. The last tube showing visible agglutination will reflect the serum antibody titer of the patient. The titer is defined as the reciprocal of the greatest serum dilution that elicits a positive agglutination reaction. Thus if serial twofold dilutions of serum are prepared and if the dilution of 1/640 shows agglutination but the dilution of 1/1280 does not, then the agglutination tier of the patient’s serum is 640.
Immuno-agglutination of latex micro-particles is used in the diagnosis of various infections, and to detect disease markers or chemical compounds in specimens of body fluids. Test-card latex particle agglutination (LPA) is usually read by eye as a qualitative indicator in medical diagnostic laboratories, although quantitative assays that rely on turbidimetric methods can determine analyte concentration.
Competitive Immunoglutination:
–Inhibition Mode
Cohen (US 4,851,329) discloses agglutination reactions performed in inhibition modes. In one embodiment, antigen-coated spheres and antibody are mixed with a test sample containing an antigen. The degree to which the antigen in the test sample inhibits the aggregation of the carrier particles, that would otherwise have occurred, indicates the concentration of antigen present. In a separate embodiment, Cohen teaches that the agglutination reaciton is performed where the antibody is coated onto to spheres and antigen is mixed with a test sample containing antibody. The degree to which the antibody present in the sample inhibits the aggregation of the carrier particles, which would otherwise have occurred, indicates the concentration of antibody present.
Mochida (US 4,332, 788) also teaches a method for determining an antigen or antibody in a sample by causing an antigen-antibody reaction among a sensitized carrier particle which is formed by binding an antigen or antibody to a carrier composed of particles, a substance such as an antigen or antibody to be determined and an agglutinating agent which is an antigen or antibody in wich the antigen or antibody to be determined inhibits the immunochemical agglutination reaction of the insoluble carrier particles with the agglutinating agent.
Kojima (US 12/438035) disclose a method for determination of an antigen or an antibody against the antigen in a sample by mixing the same with a set of reagents, the first member of the set being an antibody and the seonc member being an antigen supported on microparticles wherein a decrease in agglutination indicates that antigen is present in the sample. In a separate embodiment, Kojima teaches that the antibody is supported on microparticles and that a decrease in agglutination indiates that the antibody is present in the sample and wherein an increase in agglutation indicates that antigen is present in the sample.