Quick Review Cards for Medical Laboratory Science

Agglutination Methods Immunology Review 388

METHOD

Direct agglutination

Hemagglutination

Passive (indirect)

agglutination

Reverse passive

agglutination

Agglutination

inhibition

Hemagglutination

inhibition

Coagglutination

Antiglobulin-mediated

agglutination

PRINCIPLE

Naturally occurring ags on particles (e.g., bacterial ags). Particles

agglutinate in presence of corresponding ab.

Ag-ab rxn that results in clumping of RBCs.

Soluble ags bound to particles, e.g., latex. Particles agglutinate in

presence of corresponding ab.

Ab attached to carrier particles. Particles agglutinate in presence of

corresponding ag.

Competition between particulate ag (reagent) & soluble ag (in spec-

imen) for sites on reagent ab. Lack of agglutination is pos result.

Detects abs to certain viruses that agglutinate RBCs. In presence of

ab, virus is neutralized & hemagglutination doesn’t occur.

Reagent ab attached to carrier bacteria. (Staphylococcus aureusmost

frequently used as carrier. Protein A binds Fc portion of reagent ab.)

Visible agglutination in presence of corresponding ag.

Detection of nonagglutinating ab by coupling with 2nd ab (antihuman

globulin).

APPLICATION

Widal test for typhoid fever. Salmonella

O & H ags used to detect abs in patient

serum. Test no longer common in U.S.

ABO slide typing.

Rheumatoid factor, antinuclear antibody.

Rapid ID of bacteria.

Detection of illicit drugs.

Rubella & other viruses.

Rapid ID of bacteria.

Direct & indirect antiglobulin tests.

Notes: Rheumatoid factor can cause false-pos rxn in agglutination tests because it reacts with any IgG. Heterophile antibodies can cause false-pos rxn in hemagglutination tests.