ABO Blood Grouping Principle and Procedure

In this ABO blood grouping principle and procedure post we have briefly explained about principle, requirements, reagents, procedure, and observation.

The presence or absence of inherited antigenic compounds (antigens) on the surface of red blood cells determines blood type analysis (also known as blood grouping). The blood was classified as type A if just the “A” antigen was present on the red blood cell.
The blood was classified as type B if just the “B” antigen was present on the red blood cell. Type AB blood was defined as having a mixture of both antigens in the red blood cell. If a red blood cell lacked both antigens, the blood was classified as type O.
Antibodies are produced in response to a foreign substance in biological terms. Anti-B antibodies are present in type A blood because the immune system perceives type B red blood cells as foreign. Anti-A antibodies can be seen in type B blood. There are no antibodies against type A or B antigens in type AB. Antibodies to both type A and B antigens can be found in type O blood.

Principle

This test is based on the antigen antibody complex formation between the antigen present on the RBC and the antibody present in the serum.

Clean the slides and mark three points as A, B and D. Clean one of the fingers by rubbing with cotton soaked in rectified spirit.
When the finger dries, prick the tip of the finger with the sterile needle so that blood comes out. Put one drop of blood each near the points A, B and D.
Put one drop of anti-serum A, B and D on the blood drops near the points A, B and D respectively.
Mix the liquids at each of the three points with the wooden ends of three separate clean matchsticks.

If blood near point A agglutinates, then the blood group is ‘A’.
If blood near point B agglutinates, then the blood group is ‘B’.
If blood near both the points A and B agglutinate, then the blood group is ‘AB’.
If neither of blood near point A or B agglutinates, then the blood group is ‘O’.
If blood near point D agglutinates, then the blood group is ‘Rh positive’, else it is “Rh negative’.

The slide method can be used to test blood collected via finger puncture. To avoid clotting, the antisera should be circulated swiftly through the collected blood (on the slide).