The document discusses agglutination tests, which detect antibodies or antigens by causing particulate substances like blood cells or bacteria to clump or agglutinate when combined. There are several types of agglutination tests, including direct/active tests where antigens are naturally present on cells/bacteria, indirect/passive tests where known antigens are attached to carriers to detect unknown antibodies, and reverse passive tests where known antibodies are attached to carriers to detect unknown antigens. Common applications of agglutination tests include blood typing, detecting infections like typhoid or brucellosis, and diagnosing conditions like pregnancy or rheumatoid factor.

1. Agglutination test(lab 6)
M.Sc,Taher Badraddin
Agglutination test:interaction between antibody and a
particulate(insoluble) antigen results in visible clumping
called agglutination(Ag-Ab complex or Ag-Ab reaction)
Agglutination test: antibodies can aggltinate
multivalent particulate antigen such as red blood
cells(RBCs) or Bacteria which directly visible by naked
eye
Some virus also have the ability to agglutinate with
RBCS this behavior called agglutination
Serologic tests based on agglutination usually more
sensitive than precipitation method.
Particulate antigen include:
a- Bacteria cell c-latex particles

2. b- Red blood cell d-carbon particles
Agglutination test
Principle: The reaction between a particulate antigen
and an antibody to form cross-linking results in large
visible clumping when the corresponding specific
antibody is present in the serum called agglutination.
Antibodies that produce such reactions are known as
agglutinins. When the antigen is an erythrocyte(RBCS)
we depend on it in daignosis it is called
hemagglutination method.
Methods for Ag-Ab detection daignosis
1-Precipitation.
2-Agglutination.
3-Hemagglutination.
4-viral neutralization.
5-Radio –immunoassays.
6-ELISA.
7-Immunofluorescence.
8-Immunoblotting.
9-Immunochromatography.

3. Type of agglutination:
1. Active(direct) agglutination –Antigens found
naturally on cell surface like RBCS,Bacteria.
2. Passive(indirect) agglutination–Known antigen is
attached to a particulate “carrier,” looking for
unknown antibody(sample).
3. Reverse passive agglutination –Known antibody is
attached to a particulate “carrier,” looking for
unknown antigen(sample)
Agglutination types test
1-Active (direct) agglutination
A-Slide agglutination test
on a clean slide ,place suspension of (unknown)
blood or serum ag (contain organism) then add to it
of known antiserum then mix well ---------clumping
positive Ag-Ab complex
no clumping Negative NO Ag-Ab complex
This test is commonly used in blood grouping.

4. Principle: combination of an insoluble particulate
antigen with its soluble antibody forms antigen-
antibody complex particles clump/agglutinate used for
antigen detection.
In this reaction, the antigen is an main component
(natural self Ag) (antigens are found naturally) of the
RBCs or bacteria.
the agglutination direct method occurs due to presence
of antibody in kit against bacterial cell’s antigen or
RBC’s antigen in biological fluids(serum,csf, blood).
Example direct Agglutination test
A-It is used for blood grouping and cross- matching
before blood transfusion.
B-methodused for daignosis infection or disease such as
Widal test( Salmonella bacteria serotyping) for
diagnosis of typhoid fever. (O antigen for LPS
(somatic) , H antigen (flagellar)
C-Brucella bacteria agglutination test for Brucellosis
2-Passive (Indirect) Agglutination : is an agglutination
test done with a soluble antigen coated onto a particle
(Ag is fixed to a solid surface).
Example
a-Pregnancy test
b-Rheumatoid factor (RF)
C- ASOT test
d-C-reactive protein
-In latex agglutination procedures , sample contain
specific antibody or Antigen can coats or bound
surface of latex particles(kit) .
- If an antigen is present in a test specimen such as

5. C-reactive protein, the antigen will bind to the
combining sites of the antibody exposed on the
surface of the latex beads, forming visible cross-
linked aggregates of latex beads and antigen.
- In some procedures (e.g., pregnancy testing,
rubella antibody testing), latex particles can be
coated with antigen. In the presence of serum
antibodies, these particles agglutinate into large
visible clumps which called (reverse passive
agglutination)

6. In this sample mean positive CRP due to Ag-Ab
agglutination
3-Hemagglutination method: iagglutination that involves red
blood cells (RBCs). It has two common uses in the laboratory:

7. a- Blood typing (Direct)
Blood type can be determined by using antibodies that bind to
the A or B blood group antigens in a sample of blood. • For
example, if antibodies that bind the A blood group are added
and agglutination occurs, the blood is either type A or type
AB.
• To determine between type A or type AB, antibodies that
bind the B group are added and if agglutination does not
occur, the blood is type A.
• If agglutination does not occur with either antibodies that
bind to type A or type B antigens, then neither antigen is
present on the blood cells, which means the blood is type O
b- Quantification of virus dilutions in a Haemagglutination
assay.