What is the meaning of A1 blood group?

The A1 blood group is a subtype of the ABO blood group system, specifically referring to individuals with type A blood who have a specific genetic variation. In the ABO system, the presence of A antigens on red blood cells categorizes blood as type A, while the A1 subgroup is characterized by a stronger expression of these antigens compared to the A2 subgroup. This distinction can have implications in blood transfusions and organ transplants, as compatibility is critical for successful outcomes.