Agglutination Tests: Types, principle and uses

When the specific antibodies (agglutinins) bind to surface antigens of bacteria/virus or any antigens immobilized in particulate matter (such as latex particle) and cause the formation of a visible clumps, such test is called agglutination test.

Agglutination test can be performed in:

  • Surface of glass slides: Rapid reading/evaporation
  • Test tubes: More sensitive because of longer incubation

Reagents available commercially

Types of Agglutination..

  • Identification of an organism with known antibodies
  • Identification of serum antibodies with known antigens.

Bacterial agglutination test

  1. Measure the antibody produced by the host against bacterial agglutinins
  2. Best performance when used in sterile physiologic saline


Disease diagnosis: bacterial agent is difficult to cultivate in vitro. Some examples of such diseases are:

  1. Tetanus: Clostridium tetani
  2. Yersiniosis: Yersinia pestis
  3. Leptospirosis: Leptospira spp.
  4. Brucellosis: Brucella spp
  5. Tularemia: Francisella tularensis
Widal Test: Sample showing H positive in screening test
Widal Test is one of the most common agglutination test method

Slide Agglutination test

  • Use of Antisera (Ab)
    • to identify Salmonella and Shigella by causing agglutination of the organisms
  • Diagnostic purpose (Hospital laboratories): Antisera directed against the cell wall O antigens of Salmonella and Shigella
  • Epidemiologic purpose (Public health laboratories): Antisera against flagellar H antigen and capsular Vi antigen of salmonella.

Particle agglutination test

  1. Agglutination of an artificial carrier particle with specific antigen bound to its surface
    1. Size of the carrier enhances the visibility of agglutination.
  2. Examples include
    1. Latex particles: Latex agglutination test
    2. Treated  Red blood cells i.e. Hemagglutination
    3. Whole bacterial cells.
  3. Reaction is dependent on
    1. Amount and avidity of antigen bound to carrier
    2. Time of the incubation with specimen
    3. Environment of interaction (pH, Protein concentration etc)


  1. Treated animal RBC is used as a carrier of antigen
  2. Passive hemagglutination:  Ag that are being bound by Ab are not the Ag of RBC but are passively bound Ag.
  3. Examples
    1. Microhemagglutination test for Syphilis (MHA-TP)
    2. Hemagglutination treponemal test for Syphilis (HATTS)
    3. Passive hemagglutination tests for antibody to extracellular antigen of Streptococci
    4. Rubella indirect hemagglutination test
    5. Hemagglutination Inhibition Test (HAI) for Avian Influenza
    6. Quantitative Micro Hemagglutination Test (HA)

Latex agglutination test for Ag detection

  1. Latex beads coated with specific antibody are agglutinated in the presence of homologous antigen (bacteria).
  2. Used to determine the presence of capsular antigen of
    1. H. influenzae
    2. N. meningitidis: rapid detection of meningococcal capsular polysaccharides in CSF.
    3. Streptococcus spp.
    4. C. neoformans

Latex agglutination test for Ab detection

  1. Latex particles coated  with specific antigen
  2. Commercially available for the accurate and sensitive detection of antibody to
    1. Cytomegalovirus
    2. Rubella virus
    3. Varicella-zoster virus
    4. Heterophile antibody of infectious mononucleosis
    5. Teichoic acid antibodies of Staphylococci
    6. Antistreptcoccal antibodies
    7. Mycoplasma antibodies
    8. And others..

Coagglutination (COAG)

Coagglutination Test
Coagglutination Test

Specific antibody is bound to the surface protein A of staphylococci (Cowan type 1 strain of Staphylococcus aureus). Soluble microbial antigen in the specimen is mixed with the COAG reagent, resulting in the agglutination of the staphylococcal cells.

Antibody COAG Reagent + Antigen in specimen = Staphylococcal cells (Agglutinated)


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