It is important and useful for blood transfusion, Identifying blood diseases, for paternity tests in medico legal cases and also in anthropological studies.

Selection of blood for safe transfusion: –

It is preferable for patients to receive blood and plasma of the same ABO and Rh group. However if the required blood type is unavailable, a patient may be given a product of an alternative but compatible group as shown below.

Since O Rh Negative (O-) red cells have neither ABO nor Rh antigens on their surface, O Rh Negative red cells can be used in emergency situations. When life saving transfusion is required prior to completion of cross match, O Rh negative red cells can be used.


Group O is often referred to as the universal red cell donor due to the absence of antigens on its surface. Group AB individuals have neither anti-A nor anti-B antibodies in their plasma therefore group AB plasma can be given to patients of any ABO blood group and AB blood group is often referred to as the universal plasma donor.