Saul is rushed to the hospital after losing control at the wheel and crashing his car into a tree. His sister, Adiela, arrives at the hospital on hearing the news of the accident. The doctors ask Adiela her blood type as Saul is in need of an immediate blood transfusion. Saul's blood type is AB-positive and Adiela claims that her blood type is A-positive. The doctors decide to proceed with the blood transfusion using Adiela's blood. Why have the doctors agreed on using Adiela's blood for the transfusion?

Four major type of human blood are A, B, AB and O. The presence of sugar on the surface of RBC determines the type of blood group. N-acetylglucosamine sugar is present on the individual with A type blood group and galactose sugar is present on the surface of RBC on the individual with type B blood group. The AB individual contains both sugar residue and no sugar residue is present on type blood group O.

Saul is rushed to the hospital and needs blood transfusion. Doctor's agreed that Adiela can give her blood because Saul blood type is AB positive. No antibodies are present on her blood and both A and B antigen are present in her blood group. Adiela has blood group A+ and can donate to AB individual as she carries the A antigen on her blood cell surface.