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Blood groups and compatibility

When a transfusion is given, it is preferable for patients to receive blood of the same ABO and Rh(D) group.(1)

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 is the ABO group?

A and B are different antigens on the surface of the red cells. Antigens are proteins or carbohydrates which our immune system can recognise as foreign. O cells do not have either antigen.(2)

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 Rh(D) or Rh factor or RH1.(3)

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.(3)

The percentage of Rh negative people varies in different countries, e.g. less than 5% of India’s population are Rh negative.

An Rh(D) negative person, with an Rh(D) antibody, will destroy any Rh(D) positive red cells they come in contact with. This may occur with a transfusion or when pregnant with an Rh(D) positive baby.(3)

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

As shown in the table above, 0 Rh(-) 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 blood group. Patients should only receive plasma which does not contain an antibody which could attack their own red cells.(4)

Antibodies are important molecules our immune system makes to help protect ourselves against foreign things such as bacteria and viruses. Antibodies can also be formed in response to different blood groups.

Group O people have both Anti-A and Anti-B so group O plasma can ONLY be given to group O patients. If group O plasma were given to a group A patient, the Anti-A will attack the patient’s group A red cells.(4)

Group A plasma contains anti-B. Group A plasma can only be given to patients who are group A or O i.e. only patients who do not have group B red cells.(4)

Group B plasma contains anti-A.  Group B plasma can only be given to patients who are group B or O.(4)

Group AB plasma does not contain any Anti-A or Anti-B. AB plasma can be given to patients who are group AB, A, B or O. Group AB donors are called “universal plasma donors” and their plasma can be safely given to any patient.(4)

Patient Group Compatible Plasma Donor
O O, AB, A, B

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Last updated May 26, 2017 at 12:32 AM
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