Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Practicals Latest Physiology Blood Group
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Blood grouping is based on type of antigen
present on the red blood cells.
There are more than 300 blood group
systems but ABO and Rh(Rhesus) are of
importance from clinical point of view.
Other blood group systems are MNS ,
Lutheran , Kell , Lewis , Duffy , Kidd etc.
Discovered by Karl Landsteiner in1900.
The red cells contain different types of
Antigen(Agglutinogen) while plasma
contains antibody(Agglutinins)
Genes that control the system are present
on chromosome 9
LANDSTEINER'S LAW
If an antigen(Ag) is present on a patient's RBC,
the corresponding antibody(Ab) should not be
present in patient's plasma under normal
condition
Methods of blood grouping:
1)Slide method
2)Tube method
Tube method ?
better method
but takes longer
Sample in tube with antiserum ---
incubate it --- centrifuge it ---examine it
macroscopically and microscopically for
agglutination.
REQUIREMENTS:
1)3 slides
2)Antisera A , B
3) Blood samples
PROCEDURE:
1)
Take 2 clean slides and mark them 1, 2 .
2)
Put one drop of antisera A on slide 1 ,
one drop of antisera B on slide 2.
3)
Add one drop of blood to each and mix
well with stick
4)
Wait for 5 min and observe.
OBSERVATION:
If any agglutination occurs it is visible
with naked eyes as dark reddish clumps of
different sizes.
If agglutination is minimal it can be
confirmed by examining it under
microscope.
INTERPRETATION:
1)Agglutination with antisera A not with
antisera B ? group A
2)Agglutination with antisera B not with
antisera A ? group B.
3)Agglutination with both
antisera A and B ? group AB
4)No agglutination in any slide ? group O
Universal donor ? blood group O as no
Ag so no agglutination.
Universal recepient ? blood group AB
as both A and B Ags present so
agglutination occurs in both as no
Abs present in serum.
Rh TYPING
HISTORY:
1939 ? Levine and Stetson defined
D antigen(Rh factor)
1949 ? Landsteiner and Weiner
discovered anti Rh (named after
Rhesus monkey)
Rh TYPING
Rh blood group system is second in
significance after ABO system.
Genes that control the system are
present on chromosome 1
Consists of over 50 related Ags.
Important genes are D,C,E,c,e.
All Rh antigen are controlled by 2 genes ?
RHD gene? determines expression of D
RHCE ? encodes for C,c and E,e.
RhD is a strong antigen (immunogenic) and
other antigen are less antigenic than D and
are of less clinical significance.
Therefore , in practice Rh negative and Rh
positive depends on presence of D antigen on
the surface of red cells which is detected by
strong anti-D serum.
Occasionally, Anti - D,C,E,c,e may develop
in case of pregnancy or transfusion.
Rh positive
There is presence of D antigen.
These individuals constitute 80% of
population.
Rh negative:
There is absence of D antigen.These
individuals constitute 17% of
population.
Cc and Ee antigen:
These are weak antigens and
therefore risk of sensitisation is less
than that of D antigen.
Rh antibody:
Unlike ABO system there is no
naturally occuring antibodies against
Rh antigens in Rh negative
individuals.
Immune Abs:
Rh Abs develop against Rh Ag after
exposure to Rh Ags following
transfusion or pregnancy.
But can be detected by enzyme
treatment or coomb
test(antiglobulin test)
SIGNIFICANCE:
Rh incompartibility results in
haemolytic tranfusion reaction.
Haemolytic disease of newborn.
TECHNIQUES:
1) slide method
2)Tube method
SLIDE METHOD:
Place one drop of anti D on slide.
Add one drop of blood and mix
well with stick
Wait for 5 min and observe.
RESULT:
Agglutination indicates Rh positive
blood samples.
IMPORTANCE OF BLOOD
GROUPING AND Rh TYPING:
In blood transfusion
Haemolytic disease of newborn.
Paternity dispute
Medicolegal issues
Immunology,genetics,anthropology
Susceptibility to various
disease(blood group O ? peptic ulcer
Blood group A ? gastric ulcer)
Also known as compatibility testing.
It is the most important test before
a blood transfusion is given.
The primary purpose of cross
matching is to detect ABO
incompatibilities between donor and
recipient.
This is carried out to prevent
transfusion reactions by detecting
Abs in recipient's serum.
Two main functions of cross
matching test:
1)It is a confirm ABO compatibility
between donor and recipient.
2)It may detect presence of
irregular Ab in patient's serum that
will react with donor RBCs.
Cross matching test can be
1) major
2) minor
MAJOR CROSS MATCH TEST:
Mixing the patient's plasma with
donor RBCs.
MINOR CROSS MATCH TEST:
mixing the donor's plasma
with patient's RBCs.
SCREENING TESTS BEFORE BT:
Malaria
Syphilis
HBV
HCV
HIV
This post was last modified on 30 November 2021