BLOOD GROUP SYSTEMS
There are many blood grouping systems including ABO, Rh, Kell, Kidd, Duffy, Lutheran, Lewis, MNS. However, in routine practice, only the ABO and Rh systems are considered important.
ABO AND Rh-D GROUPING
It is the most important part of blood grouping. It can be performed on the cells as well as on the serum. When it is performed on the cells it is called direct grouping (forward typing) in which unknown red cells (test cells) are tested against known antisera. When it is performed on the serum it is called indirect grouping (reverse typing) in which the unknown serum (test serum) is tested against known red cells. Ideally, both should be performed on each specimen.
DIRECT GROUPING (FORWARD TYPING)
This can be performed either by the Tile Method or by the Test Tube Method.
The Tile Method:
1. Allow the blood to clot. Clear supernatant serum should be aspirated carefully with the help of a Pasteur Pipette into another clean tube.
2. Prepare 5% cell suspension from the cells by mixing one drop of packed cells with 19 drops of buffered normal saline.
3. Divide the tile (with a grease pencil) into A, A1, B, AB and Rh D squares.
4. Place one drop of the corresponding antiserum in each square.
5. Add a drop of test cell suspension into each of the squares that contain antiserum.
6. Mix with a glass rod, cleaning its tip thoroughly after mixing in each square.
7. Gently tilt the slide backward and forwards at room temperature for a maximum of two minutes.
8. Macroscopically read for agglutination and record the result.
9. Rh D-negative persons may be tested for Du (variant).
The Test Tube Method:
1. Prepare a 2-3% suspension of red cells in isotonic buffered saline.
2. Arrange test tubes in the rack, marked anti-A, anti-A1, anti-B, anti-AB, and anti-Rh D.
3. Add one drop of the corresponding antiserum to each of the test tubes.
4. Using a small pipette, add one drop of 2-3% cell suspension to all the test tubes.
5. Mix well and centrifuge at 3400 RPM (9001000g) for 30 seconds.
6. Try to re-suspend the cells by gentle agitation and read macroscopically for agglutination and/or hemolysis.
7. Confirm a negative result by microscopy.
8. Rh D-negative persons may be tested for Du (variant).
INDIRECT BLOOD GROUPING (REVERSE TYPING):
This can also be performed by the tile or the test- tube method.
The Tile Method:
1. Divide the tile (with a grease pencil) into the A, B, O, and auto-control squares.
2. Place one drop of the patient‘s serum in all of the squares.
3. Add one drop of the corresponding 2-3% suspension of red cells to the labeled squares.
4. Add one drop of the 2-3% suspension of the patient‘s red cells to the square labeled. auto-control.
5. Mix well with a glass rod, cleaning its tip after each application. Gently tilt the slide backward and forwards at room temperature for a maximum of two minutes.
6. Macroscopically read for agglutination.
The Test Tube Method:
1. Place 2 drops of the serum to be tested into test tubes labeled A, B, O, and auto-control.
2. Using a Pasteur Pipette, add one drop of 23% suspension of corresponding cells into each tube.
3. Add one drop of test red cells (patient‘s red cells) to the test tube labeled auto-control.
4. Mix well and centrifuge at 3400 RPM (9001000g) for 30 seconds.
5. Try to re-suspend the cells by gentle agitation and read macroscopically for agglutination or hemolysis.
6. Confirm a negative result by microscopy.
