An anaphylactic or anaphylactoid reaction during transfusion of a blood component has serious implications for the patient, especially if the person continues to have blood replacement needs. An attempt should be made to identify the cause, with future blood products selected accordingly.

Causes for an anaphylactic reaction during a blood transfusion:

(1) antibodies to IgA, usually in an IgA-deficient person. Isolated IgA deficiency may affect 1 in 700-800 persons of European descent. However, less than 20% of these patients experience an anaphylactic reaction to a blood product.

(2) allergic reactions to other serum proteins or components in the blood product

(3) allergic reactions to drugs or chemicals received by the patient before or during the transfusion




First: Exclude other conditions in the differential diagnosis (sepsis, heart failure, hemolytic transfusion reaction, pulmonary embolus, etc.).


Second: Try to identify all possible exposures to medications and foods prior to the anaphylactic reaction.


Third: Quantitate the person's pretransfusion serum for IgA level and test for anti-IgA antibodies.

(1) A person is considered IgA-deficient if serum IgA levels are < 0.05 mg/dL (this is much less than the level used to diagnose selective IgA deficiency).

(2) Not all patients who are IgA-deficient and who have anti-IgA antibodies will have an anaphylactic reaction on exposure to normal blood components.

(3) A person who is not IgA-deficient may have anti-IgA antibodies. This may occur as an autoantibody or due to variation in the person's IgA from normal.

(4) Measurement of IgE-type anti-IgA is preferred but may not be available.


Fourth: If anti-IgA is absent, then transfuse unwashed blood components under close medical supervision, with adequate resources to manage a serious anaphylactic reaction.


Fifth: If anti-IgA is absent and the person does not react to unwashed blood components, then evaluate any foods or medications received prior to the transfusion that was associated with the anaphylactic reaction.



Products for Future Transfusions

circulating anti-IgA antibodies

use IgA-deficient blood components

no circulating anti-IgA AND has an anaphylactic reaction to unwashed blood components

use washed blood components

no circulating anti-IgA AND no anaphylactic reaction to unwashed blood components

use standard, unwashed blood components; look for a food or drug that may have caused the reaction

components may have caused the reaction


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