Download Agglutination tests:

Agglutination tests:
1. Agglutination/Hemagglutination
 When the antigen is particulate, the reaction of an antibody with the antigen can
be detected by agglutination (clumping) of the antigen.
 The general term agglutinin is used to describe antibodies that agglutinate
particulate antigens.
a. Qualitative agglutination test
For example, a patient's red blood cells can be mixed with antibody to a
blood group antigen to determine a person's blood type. In a second
example, a patient's serum is mixed with red blood cells of a known blood
type to assay for the presence of antibodies to that blood type in the patient's
serum
.
b. Quantitative agglutination test
Agglutination tests can also be used to measure the level of antibodies to
particulate antigens
Applications of agglutination tests
1. Determination of blood types or antibodies to blood group antigens.
2. To assess bacterial infections
2-Passive hemagglutination:
Carrier particles agglutination tests using erythrocytes as carrier particles for Ab or
Ag molecules. These erythrocyte are taken from sheep, turkey and chicken.
Treated chemically and prepared to be coated by known Ag or Ag which are
commercially available.
In case where RBSc are coated with known Ags and used for detection of specific
Ab, these cases are known as Passive haemoagglutination tests.
While when RBCs are coated with specific Abs and used to detect Ags are called
Reverse Passive haemoagglutination tests.
a. Passive haemoagglutination tests:
 Diagnosis of Toxoplasma gondii.
 Diagnosis of mycoplasma pneumoniae infection.
B. Reverse Passive haemoagglutination tests
 Detection of HBs-antigen in serum
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3- Haemagglutination Inhibition
 The agglutination test can be modified to be used for the measurement of
soluble antigens. This test is called hemagglutination inhibition.
 It is called hemagglutination inhibition because one measures the ability of
soluble antigen to inhibit the agglutination of antigen-coated red blood cells
by antibodies. In this test, a fixed amount of antibodies to the antigen in
question is mixed with a fixed amount of red blood cells coated with the
antigen.
 Also included in the mixture are different amounts of the sample to be
analyzed for the presence of the antigen. If the sample contains the antigen,
the soluble antigen will compete with the antigen coated on the red blood
cells for binding to the antibodies, thereby inhibiting the agglutination of the
red blood cells.
4- FLUCCULATION TEST
It is a form of agglutination in which the Ag is found in colloidal form instead of
being particulate.
In the flocculation test the antigen –antibody complex become aggregated in small
floccules which should be read macroscopically or microscopically using a lower
power objective at a total magnificence of 100 x.
Applications:
1. VDRL or The Venereal Disease Research Laboratory test for syphilis. In
this test an antigen which is not of microbial origin. Antigens that is used is a
colloidal suspension of tissue lipid known as cardiolipin, which is a combination
between cholesterol and lecithin react with the auto-antibodies, that can be
produced by Treponema pallidum, the bacteria that causes syphilis, to form
microscopically visible floccules.
 The VDRL test's ability to detect syphilis depends on the stage of the
disease. The test's sensitivity to detect syphilis nears 100% during the middle
stages; it is less sensitive during the earlier and later stages.
 In this disease there are two types of antibodies produced, antibody which is
specifically against the Treponema pallidum, and auto antibodies against tissues
contains the organisms.
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Some conditions may cause a false positive test, including:
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HIV
Certain types of pneumonia
Malaria
Systemic lupus erythematosus
2. RPR (rapid plasma reagin) is a screening test for syphilis. It looks for
antibodies that are present in the blood of people who have the disease. The test is
similar to the venereal disease research laboratory (VDRL) test.
 In this test the reagent contains carbon in addition to cardiolipin to enhance
the difference between the negative and the positive reaction.
 It is a screening test (non specific test)
 A positive test result may mean you have syphilis. If the test is positive, the
next step is to confirm the results with an FTA-ABS test, (The fluorescent
treponemal antibody absorption) test measures a specific antibody made against
Treponema pallidum.
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