How is the ABO blood group determined?

The classification of blood into the ABO system relies fundamentally on the presence or absence of specific antigens on the surface of red blood cells. In this system, there are four main blood types: A, B, AB, and O. The blood type is determined by the type of antigens present:

• Type A has A antigens on the red blood cells and anti-B antibodies in the plasma.

• Type B has B antigens on the red blood cells and anti-A antibodies in the plasma.

• Type AB has both A and B antigens and no anti-A or anti-B antibodies.

• Type O has neither A nor B antigens and contains both anti-A and anti-B antibodies.

Identifying these antigens is crucial because they play a significant role in blood transfusions and organ transplants; mismatched blood types can lead to serious and potentially fatal immune reactions. Therefore, analyzing the antigens present on the red blood cells is the precise method used to determine a person's ABO blood group. This multifunctional characteristic is key in medical settings for ensuring compatibility during blood transfusions and surgeries.