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Coombs Test

The document discusses the Coombs test, which includes direct and indirect antiglobulin tests used to detect antibodies bound to red blood cells. The direct antiglobulin test identifies red cell sensitization in vivo, while the indirect test detects immune antibodies in patient serum due to transfusion or pregnancy. Both tests involve specific procedures to observe agglutination as an indicator of antibody presence.

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36 views8 pages

Coombs Test

The document discusses the Coombs test, which includes direct and indirect antiglobulin tests used to detect antibodies bound to red blood cells. The direct antiglobulin test identifies red cell sensitization in vivo, while the indirect test detects immune antibodies in patient serum due to transfusion or pregnancy. Both tests involve specific procedures to observe agglutination as an indicator of antibody presence.

Uploaded by

falase.o.damilola
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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COOMBS TEST

MLSC 336

TUNDE
FA K O YA
Direct and indirect antiglobulin test
❑Antiglobulin test is based on anti-human antibodies binding to human antibodies,
commonly IgG or IgM.

❑These anti-human antibodies are produced by plasma cells of non-human animals after
immunizing them with human plasma.

❑ Anti-human antibodies will also bind to human antibodies that may be fixed
onto antigens on the surface of red blood cells (rbcs).

❑It is also referred to as Coombs test


Direct and indirect antiglobulin test
There are two types of antiglobulin test
oDirect antiglobulin (DAT)
oIndirect antiglobulin test (IAT)

Antiglobulin techniques are used to detect cells coated with incomplete antibodies, for
antibody screening before transfusion, antibody detection in post transfusion reactions and
other reactions such as hemolytic disease of the newborn, hemolytic anaemias
Direct anti-globulin test
The direct coombs test, also referred to as the direct antiglobulin test (DAT), is used to detect
red cell sensitization by antibodies or complement system factors bound to surface antigens
in-vivo
Principle: Red cells coated with complement or IgG antibodies are agglutinated by additional
antibody which forms a bridge between the antibodies coating the red cell causing
agglutination
Technique: Prepare a 5% suspension of patient red cells.
To one drop of the red cell suspension add 2 drops of Antihuman globulin
Mix gently and centrifuge at 1000g for 60 seconds
Observe the mixture for agglutination.
DIRECT ANTIGLOBULIN TEST
Indirect antiglobulin test
Indirect antiglobulin test is useful for the detection of immune antibodies in the
patient serum formed as a result of sensitization by transfuse on or pregnancy.
This procedure involves 4 steps
a. Incubation of control red cell and test serum at 37 degrees for red cell sensitization
b. Washing of red cell to remove excess free antibodies in the suspension
c. Reaction with Anti human globulin
d. Result visualization for agglutination
Indirect antiglobulin test
Principle: Immune antibodies are detected in vitro by initial sensitization with red cell and subsequent
formation of agglutination using antibodies to the immune antibody
Mix one drop of 5% O rhesus D positive cell suspension with 2-3 drops of patient serum
Incubate at 37 degrees for 45-60 minutes
Centrifuge at 1000g for 60 seconds
Observe mixture for agglutination or hemolysis
Wash the cells three times to remove excess supernatant
Resuspend cells and add 2 drops of antihuman globulin
Mix gently and centrifuge at 1000g for 60 seconds
Observe the mixture for agglutination.
INDIRECT ANTIGLOBULIN TEST

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