Transfusion Therapy - Blood Typing and Cross-Matching
Donor blood and recipient blood
Donor blood and recipient blood are typed using the red cell surface ABO and Rh systems and screened for antibodies to other cell antigens. “Direct” cross-matching involves directly mixing the patient's plasma with the donor's red cells to establish that hemolysis does not occur from any undetected antibodies. An individual's red cells have A, B, AB, or no surface antigens, which is then designated type O. If the patient's red cells are lacking either surface antigen A or surface antigen B, then antibodies will be produced against it. A person who is type B will have anti-A antibodies in the serum, and a type O individual will have circulating anti-A and anti-B antibodies. Consequently, a person who is type AB will not have antibodies to either A or B and can receive red blood cells (RBCs) from any blood type. Type O blood has neither A nor B surface antigens and can donate blood cells to any other type (universal red cell donor; Table 35.1). The universal FFP donor, conversely, is AB because it will contain neither anti-A nor anti-B antibodies. Whole blood donors and recipients must be exact ABO matches because whole blood contains both RBCs and serum. For example, a unit of type O whole blood will contain serum with anti-A and anti-B antibodies and therefore cannot be used to transfuse patients who are A, B, or AB blood types.
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