General Knowledge about Blood  Blood Groups

There are four blood groups: A, B, AB and O.

Your blood group is determined by the group of antigen in your red cells.  Both group A refers to the fact that you have A-antigens, type B has B-antigens, blood group AB refers to the existence of both, while type O has neither A nor B.

These four blood types were originally identified by Karl Landsteiner in 1900. In the century that has passed since, we have learnt even more about blood types.

Which types are most common and most rare?
Generally speaking, blood type O is the most common worldwide, but this varies according to ethnicity and geographical location. In Hong Kong, 40% of the population is type O, while types A and B are represented by about 26% of the population respectively. Interestingly, only 7% of Hong Kong’s population is type AB. Elsewhere in China, Beijing's population shows somewhat different results. Just 29% of the population there is type O, while types A and AB can be found in 27% and 13% of the population respectively. Overall in Beijing, type B is the most common blood type, found in 32% of residents.

Which blood types is the “universal donor” and which is the “universal recipient”?
People having blood type O are commonly known as “universal donors”, while those having blood type AB are “universal recipient”. As blood contains antigens and naturally occurring antibodies that have to be matched between donor and recipient, blood transfusion must be closely regulated. If a transfusion is given after an incompatible match, a condition of haemolysis can set in, resulting in the recipient’s blood losing its ability to carry nutrients and oxygen. In some cases, this may even be life-threatening. Chart 1 shows which blood types are compatible. However, with advances in medical knowledge and research, it should be remembered that blood types are now not the only concern when transfusion blood.

(Chart 1)

Rumor 1 : All children have the same blood group as either their father or mother.

Not necessarily.  Since children can inherit different antigens from each parent, there is a chance that they will not have the same blood type as either parent.  Chart 2 shows the blood group variations that can occur in children.

(Chart 2)

Rumor 2 : Blood ties can be proven by mixing the blood of two people

By mixing incompatible blood types, an agglutinative reaction from the incompatibility between antigens and antibodies can be observed.  Yet this proves little, since blood group O will have an agglutination reaction when mixed with any blood type other than itself and, as shown in the chart, it is perfectly feasible that offspring can inherit different blood types than their parents.  Many relatives also share the same blood group. Therefore, the method of “mixing blood” to establish blood ties is unreliable.  Today, DNA testing is the only accurate way of verifying family bonds.

So are you my type?

The simplest and easiest way to know your blood type is to donate blood, because first-time blood donors receive a memorial badge indicating their blood type.  Even more importantly, donating blood is a great way to help those in need.  Why not do it today?