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16.6D: Typing and Cross-Matching for Transfusions

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  • Blood banks test donor blood to ensure recipient compatibility, reducing the risk of hemolytic reaction, renal failure, and death.

    Learning Objectives

    • Explain the purposes of typing and of cross-matching blood prior to transfusion

    Key Points

    • Transfusion medicine is important to treat those with blood loss.
    • Given enough time, cross-matching is performed to ensure that donated blood will not cause a transfusion reaction.
    • Cross-matching involves mixing a sample of the recipient’s serum with a sample of the donor’s red blood cells and checking if the mixture agglutinates due to antibody reactivity.
    • If a transfusion with non-matched blood occurs, the patient risks red blood cell destruction, renal failure, shock, and death.

    Key Terms

    • hemolysis: The destruction of red blood cells from pathological causes, such as infection or immune system mediated damage.
    • agglutinate: The act of red blood cells clumping together due to antibody reactivity.

    Transfusion medicine is extremely effective at treating those with severe blood loss. Transfusions are often a required component of major surgeries. Due to the different antigen blood types, blood must be cross-matched during processing to avoid potential complications.

    The Cross-Matching Process

    Much of the routine work of a blood bank involves testing blood from both donors and recipients to ensure that every recipient is given blood that is compatible and is as safe as possible. Several laboratory tests allow cross-matching of compatible blood between donor and recipient. Patients should ideally receive their own blood or type-specific blood products to minimize the chance of a transfusion reaction. Risks can be further reduced by cross-matching blood, but this process isn’t always performed if time is short and the need for transfusion has not been anticipated.


    Agglutinated RBC: Red blood cells can agglutinate if the serum contains antibodies against the expressed proteins. In this image, the blood serum contains anti-A3 antibodies, which attack and agglutinate type A blood.

    Cross-matching involves mixing a sample of the recipient’s serum with a sample of the donor’s red blood cells and checking if the mixture agglutinates, or forms clumps. These clumps are the result of antibodies binding the red blood cells together. If agglutination is not obvious by direct vision, blood bank technicians check for agglutination with a microscope. If agglutination occurs, that particular donor’s blood cannot be transfused to that particular recipient. In a blood bank, it is vital that all blood specimens are correctly identified, so labeling has been standardized using a barcode system known as ISBT 128. The blood group may be included on identification by military personnel in case they need an emergency blood transfusion.

    Potential Transfusion Complications

    If a patient receives blood during a transfusion that is not compatible with his or her blood type, severe problems can occur. Acute hemolytic transfusion reactions occur if donated blood cells are attacked by matching host antibodies. This can cause shock-like symptoms, such as fever, hypotension, and disseminated intravascular coagulation from immune system mediated endothelial damage. Transfusion reactions are also associated with acute renal failure. Lung injury is common as well, due to pulmonary edema from fluid overload if plasma volume becomes too high or neutrophil activation during a transfusion reaction. If the donated blood is contaminated with bacteria, it may induce septic shock in the patient.



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