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
- Measure the antibody produced by the host against bacterial agglutinins
- Best performance when used in sterile physiologic saline
Disease diagnosis: bacterial agent is difficult to cultivate in vitro. Some examples of such diseases are:
- Tetanus: Clostridium tetani
- Yersiniosis: Yersinia pestis
- Leptospirosis: Leptospira spp.
- Brucellosis: Brucella spp
- Tularemia: Francisella tularensis
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
- Agglutination of an artificial carrier particle with specific antigen bound to its surface
- Size of the carrier enhances the visibility of agglutination.
- Examples include
- Latex particles: Latex agglutination test
- Treated Red blood cells i.e. Hemagglutination
- Whole bacterial cells.
- Reaction is dependent on
- Amount and avidity of antigen bound to carrier
- Time of the incubation with specimen
- Environment of interaction (pH, Protein concentration etc)
- Treated animal RBC is used as a carrier of antigen
- Passive hemagglutination: Ag that are being bound by Ab are not the Ag of RBC but are passively bound Ag.
- Microhemagglutination test for Syphilis (MHA-TP)
- Hemagglutination treponemal test for Syphilis (HATTS)
- Passive hemagglutination tests for antibody to extracellular antigen of Streptococci
- Rubella indirect hemagglutination test
- Hemagglutination Inhibition Test (HAI) for Avian Influenza
- Quantitative Micro Hemagglutination Test (HA)
Latex agglutination test for Ag detection
- Latex beads coated with specific antibody are agglutinated in the presence of homologous antigen (bacteria).
- Used to determine the presence of capsular antigen of
- H. influenzae
- N. meningitidis: rapid detection of meningococcal capsular polysaccharides in CSF.
- Streptococcus spp.
- C. neoformans
Latex agglutination test for Ab detection
- Latex particles coated with specific antigen
- Commercially available for the accurate and sensitive detection of antibody to
- Rubella virus
- Varicella-zoster virus
- Heterophile antibody of infectious mononucleosis
- Teichoic acid antibodies of Staphylococci
- Antistreptcoccal antibodies
- Mycoplasma antibodies
- And others..
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)