Food-allergic reactions require:
(1) absorption of intact food allergen from gastrointestinal tract
(2) sufficient concentration of the food allergen in the donor blood to trigger an allergic reaction
(3) a transfusion recipient with a significant allergy to the allergen
While most potential allergens would be cleared relatively quickly, a protein might persist for some time. If the donor had a diet high in that food, then accumulation in the blood serum could occur.
The diagnosis requires:
(1) a clinical need to establish cause (such as an anaphylactic reaction)
(2) pre- and post-transfusion blood samples from recipient
(3) pre-transfusion blood sample from donor
(4) contact with donor
(5) donor recollection of diet prior to blood donation
(6) contact with the recipient
(7) exclusion of other causes for allergic reaction (drugs, passive transfer of donor IgE antibodies to recipient)
Factors that can help to establish the diagnosis:
(1) The recipient has a known food allergy to a food that the donor recalls.
(2) There is a rise in IgE in post-transfusion recipient serum compared to a pre-transfusion sample.
(3) RAST or other testing for common food allergies can be performed on pre- and post-transfusion serum samples from the recipient.
(4) Demonstration of the food allergen in the donor's serum.
Barriers to the diagnosis:
(1) The recipient has received multiple blood products.
(2) A time interval between blood donation and testing is long and the allergen is no longer present in the donor's blood.
