Which cells are primarily checked for incompatibility before a blood transfusion?

Before a blood transfusion, the primary focus is on red blood cells. This is because the red blood cells contain antigens on their surface that can trigger an immune response if they are incompatible with the recipient's blood type. The major blood group systems, such as ABO and Rh, are determined primarily by these red blood cell antigens.

When a patient receives a transfusion, it's crucial to match the donor’s red blood cells with the recipient's to prevent potential complications like hemolytic reactions, which occur when the recipient's immune system attacks the transfused red blood cells due to incompatibility. The presence of specific antibodies in the recipient’s plasma against the donor's red blood cell antigens can result in severe reactions if not properly matched.

In contrast, white blood cells, platelets, and plasma primarily play different roles in the body and in various transfusion processes. While white blood cells can also be involved in immunological reactions, blood transfusion compatibility primarily centers around the red blood cells due to the immediate and severe risks associated with incompatibility in this context.