ABO and Rh Typing: Introduction, Principle, Test Requirements, Procedure, Result-Interpretation, Applications, and Keynotes
ABO and Rh Typing-Slide Method
Introduction of ABO and Rh Typing
Table of Contents
ABO blood grouping and Rh typing are the most common blood group systems. There are nearly 300 blood group systems so far discovered. Other than ABO and Rh are MNS, Lutheran, Kell, Duffy, etc. Karl Landsteiner discovered ABO ( A, B and O) in 1900. Two years later, Decastello and Sturli added AB and finally ABO system gets completed. In 1940, Karl Landsteiner and Winner discovered Rh factor in red blood cells (RBCs) of the Rhesus monkey (Macca rhesus).
Principle of ABO Blood Grouping and Rh Typing
ABO blood grouping and Rh typing work on the principle of agglutination. The normal red blood cells possessing antigens will clump in the presence of corresponding antibodies.
Methods of ABO and Rh Typing
Slide
Tube
Note: Here we are concerned with the slide method of ABO blood grouping and Rh typing.
Preparation of 10% RBCs suspension in normal saline-Mix 5 drops ( 50µl each) of sedimented RBCs with 2 ml of normal saline. Centrifuge at 1500 RPM for 1 minute and discard the supernatant. Put 2 ml of normal saline into the sedimented RBCs and mix it well. This preparation gives a 10% suspension of RBCs.
Take a glass slide in which place a drop of antisera-A on one half and a drop of antisera-B on the other half.
Take another glass slide and place a drop of antisera-D at the centre.
Using a pipette or dropper add a drop of the RBCs suspension to all separate antisera.
Mix each cell and antisera using separate applicator sticks.
Tilt the glass slide back and forth for up to 2 minutes.
Observe for agglutination or clumping.
Result and Interpretation of Blood Grouping
For the ABO blood group system
Clumping on antisera-A but not B: Blood group A
Agglutination or clumping on antisera -B but not A: Blood group B
Clumping on both antisera A and B: Blood group AB
No clumping on both antisera-Aand B: Blood group O
For Rh typing
Clumping on antisera-D: Positive
No clumping on antisera-D: Negative
Fig. ABO and Rh Typing-Slide Method
Applications Blood Grouping and Rh Typing
It is applicable to the following fields-
Prior to blood transfusion
In the case of hemolytic disease of the newborn (HDN)
Determination of paternity in medico-legal cases
Relationship of blood groups, susceptibility to various diseases e.g. blood group A is more prone to gastric carcinoma whereas blood group O is more prone to systemic lupus erythematosus.
Keynotes
Blood obtained from finger-prick may be tested directly by the slide method quickly without making 10% RBCs suspension to avoid clotting and drying.
A test that shows no agglutination within 2 minutes is considered negative.
Never interpret peripheral drying as fibrin stands as clumping.
Rh factor is found in 85% of people.
Blood group % in US population are A-41%, B-9%, AB-4% and 0-46%.
Blood group % in Indian population are A-27%, B-31%, AB-8% and 0-34%.
Blood group% in Nepales population are A-33%, B-27%, AB-12% and 0-28%.