24th Page Flashcards
(32 cards)
What is agglutination?
A process by which particulate antigens such as cells aggregate to form larger complexes when a specific antibody is present.
What are the steps involved in agglutination?
SL
- Sensitization
- Lattice Formation
The first reaction involves Ag-Ab combination through SINGLE antigenic determinants on the particle surface.
Sensitization
The sum of interactions between antibody and MULTIPLE antigenic determinants on a particle depends on environmental conditions and the relative concentrations of Ag and Ab.
Lattice Formation
What are the types of agglutination reactions?
- Direct agglutination
- Passive agglutination / Indirect agglutination
- Reverse passive agglutination
- Coagglutination
- Agglutination inhibition
- Hemagglutination inhibition
What is direct agglutination?
Agglutination where antigens are found NATURALLY on a particle.
Example: Kauffmann and white scheme (Widal Test) for Salmonella serotyping.
What is hemagglutination?
Agglutination reaction that involves RBCs.
Example: ABO typing of human RBCs, test for Febrile agglutinins such as Widal.
What is passive agglutination?
Antigen is attached to a CARRIER particle such as latex, bentonite, charcoal, and RBC
Agglutination occurs if patient Ab is present.
Example: Rheumatoid factor, ASO, Antinuclear Ab and antibodies to Trichinella.
What is reverse passive agglutination?
Ab rather than antigen is attached to a carrier particle.
Agglutination occurs if patient antigen is present.
Used to detect microbial antigens.
What is coagglutination?
Uses BACTERIA as the inert particles to which Ab is attached.
S. aureus is most frequently used, because it has a protein on its outer surface (protein A), which naturally adsorbs the Fc portion of IgG molecules.
What is agglutination inhibition?
Reactions are based on competition between particulate and soluble Ags for LIMITED Ab-combining sites.
Lack of agglutination is an indicator of a positive reaction.
Example: human chorionic gonadotropin (hCG) test.
What is hemagglutination inhibition?
RBCs are the indicator particles used to detect antibodies to certain viruses.
Examples include Rubella, Mumps, Measles, Influenza, Parainfluenza, HBV, Herpes, Respiratory Syncytial virus, and Adenovirus.
What is the purpose of Antiglobulin-Mediated Agglutination / Coomb’s Test?
Detects non-agglutinating antibodies by means of coupling with a SECOND antibody.
DAT
Investigation of Hemolytic Disease of the Newborn (HDN)
Hemolytic Transfusion Reactions (HTR)
Diagnosis of Autoimmune Hemolytic Anemia (AIHA), Diagnosis of Drug-Induced Hemolytic Anemia,
IAT
CAARD
Crossmatching
Antibody Detection
Antibody Identification
RBC Antigen Phenotyping such as Du / Weak D typing.
What are the types of AHG preparation?
PM
- Polyclonal Antibodies
- Monoclonal Antibodies
prepared by conventional technology using rabbits, goats
Polyclonal Antibodies
prepared by hybridoma technology using mice as source of antibodies
Monoclonal Antibodies
What is Polyspentic AHG?
Contains anti-IgG and Anti-C3d.
What is Monospecific AHG?
Contains either anti-IgG or Anti-C3d.
What are O Check Cells?
Group O Rh positive RBC, sensitized with IgG/ Anti-D, added to negative AHG tests to validate the negative reaction.
What does a negative AHG reaction indicate?
No agglutination, which may be invalid due to reasons such as
neutralized and inactivated AHG reagent, expired AHG reagent, or
omission of AHG reagent.
What does a positive AHG reaction indicate?
Agglutination, indicating VALID TEST, done properly and there is no sensitization of patient’s antigen or RBC.
How is agglutination graded?
0: No agglutinates,
W+: Many tiny agglutinates/many free cells/ may not be visible in microscope
1+: Many small agglutinates/ many free cells
2+: Many medium-sized agglutinates/ moderate free cells
3+: Several large agglutinates/ few free cells
4+: One large, solid agglutinate/ no free cells
