Matching blood groups

Before you receive a transfusion, compatibility testing is performed between the donated blood and a patient's blood sample.

When a transfusion is given, it is preferable for patients to receive blood of the same ABO and RhD group. However, in an emergency or special circumstance, if the same blood group isn’t readily available, a patient may be given another group that their immune system will not react to.

What are antigens?

Antigens are proteins or carbohydrates which our immune system can recognise. Any antigen that is ‘foreign’ to our immune system is destroyed by an antibody.

What are antibodies?

Antibodies are attack molecules our immune system makes to protect ourselves against foreign things such as bacteria and viruses. Antibodies can also be formed in response to different blood groups. Everyone is born
with some antibodies.

What is the ABO group? 

A and B are different antigens on the surface of the red cells. O cells do not have either antigen. The type of antigen on your red cells is genetically determined. If you have the A antigen, you have Group A red cells. It is also possible to have both A and B antigens meaning your blood group is AB. 

What is Rh? 

The Rh blood group system has around 50 different red blood cell antigens. D is the most important antigen of the Rh system. It is also known as RhD. In Australia, approximately 83% of people will have the D antigen on their red cells. Their blood type is called Rh positive. The other 17% do not have the D on their red cells and are called Rh negative. The percentage of Rh negative people varies in different countries (eg. less than 5% of India’s population are Rh negative). An RhD negative person, with an RhD antibody, will destroy any RhD positive red cells they come in contact with. This may occur with a transfusion or when pregnant with an RhD positive baby. Rh is very important for women who are or may become pregnant as the antibodies can cause problems for mother and baby. 

Red cell compatibility

It is a general principle that red cell components of identical ABO group and RhD type as the recipient should be used for transfusion. 

As shown in the table below, O Rh negative is the universal red cell donor blood that can be given to all patients.

This is common practice when a patient’s blood group is unknown and in emergency situations especially for women of child-bearing age.

Plasma compatibility 

Plasma contains anti-A and anti-B antibodies depending upon the blood group. Our body also has antibodies to A and/or B antigens according to our blood group. Patients should only receive plasma that does not contain an antibody which could attack the antigens present on their own red cells.

Group A recipients have A antigen on their red cells, so they can’t receive group O or group B plasma as the anti-A will attack their red cells. Group B recipients have B antigen on their red cells, so they can’t receive group O or group A plasma as the anti-B will attack their red cells. 

Group AB recipients can only receive group AB plasma. Group O recipients do not have either A or B antigen, so can safely receive plasma of any blood group type.


Platelet Compatibility

ABO identical platelets are usually preferred. However, in some circumstances, the need for other special requirements may be more important than providing the same ABO group.

This will be determined by the health care team overseeing your care. For more information please consult with your health care team.


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