LATEX AGGLUTINATION TEST
The latex agglutination test is a laboratory
method to check for certain antibodies or
antigens in clinical laboratories for the
detection of infectious diseases such as rheumatoid
arthritis, hepatitis B, haemophilus influenza,
enisseria meningitidism, etc.
In 1956 Singer and Plotz first described the
Rheumatoid Factor Test, a test based on latex
agglutination.
In rheumatoid arthritis IgG antibodies produced
by lymphocytes in the synovial joint react
with the IgM antibodies (RF, rheumatoid factor)
to generate immune complexes that activate
the complement and cause the tissue destruction.
The reaction between a particulate antigen
and an antibody results in visible clumping
called agglutination.
Antibodies that produce such reactions are
known as agglutinins.
The principle of agglutination reactions are
similar to precipitation reactions: they depend
on the cross linking of polyvalent antigens.
When the antigen is an erythrocyte, it is
called hemagglutination.
Theoretically, all antibodies can agglutinate
particulate antigens but IgM, due to its high
specificity, is a particularly good agglutinin.
Agglutination tests employ latex particles,
gelatin beads, colloidal particles, or preserved
mammalian or avian blood cells to facilitate
visualization of agglutination.
In the latex agglutination test, the sample
to be tested is sent to the lab where it mixed
with latex beads coated with a specific antigen
or antibody.
Materials Required:
1.5 ml Vials.
Microcentrifuge.
Pipette.
Micro tips.
Laboratory refrigerator.
Glycine saline buffer.
Blocking buffer.
Antigen for coating.
Latex beads.
Test antiserum.
Glass slides.
Beaker.
Toothpick.
Procedure:
Coating of Latex
To 20 µl of latex beads taken in a 1.5 ml
vial, add 40 µl of glycine-saline buffer.
Add 60 µl of antigen to the latex and incubate
at 37oC for 2 hours.
Spin down at 5000 rpm for 10 minutes and carefully
aspirate the supernatant.
Resuspend the pellet in 1 ml of blocking buffer
and spin down at 5000 rpm for 10 minutes.
Repeat the washing once more.
Add 90 µl of blocking buffer to the pellet,
mix well.
Incubate at 40C, overnight.
Agglutination Test:
To 200 µl of glycine-saline buffer taken
in a vial, add 4 µl of test antiserum (50
times diluted).
Add 50 µl of antigen to 50 µl of diluted
antiserum in a 1.5 ml vial, mix well and incubate
at room temperature for 10 minutes.
Pipette 10 µl of coated latex on a glass
slides.
Add 10 µl of diluted test antiserum to slide
A.
Add 10 µl of antiserum mixed with antigen
(from step 8) to B.
Add 10 µl of glycine-saline buffer to C.
Take a toothpick and mix the contents on each
slide.
Discard the toothpick after using it for one
slide and use a new one for the next slide.
After mixing, wait for 2 minutes to observe
the result.
Result:
The clumping of latex beads (agglutination)
indicates the presence of suspected particles.
Absence of white clumps indicates a negative
result, i.e., the suspected particle is not
present.
ADVANTAGES:
Helps in detecting certain antigens or antibodies
in a variety of bodily fluids such as blood,
saliva, urine or cerebrospinal fluid.
Ability to obtain semi-quantitative results.
A low individual test cost.
Relatively short time to obtain results.
