Diagnosis of allergic reactions is based on the recognition of a skin rash associated with itching. Treatment involves temporarily discontinuing the transfusion and administering an antihistamine. The rash will usually heal when the transfusion is stopped or when an antihistamine is given. Once symptoms have been alleviated, the transfusion may be resumed. If symptoms continue or progress, the transfusion must be stopped and a new donor unit obtained. Premedication with antihistamine will usually prevent urticarial reactions in patients with a history of allergic reactions. If premedication is unsuccessful, washed cellular products may prevent a reaction. Leukoreduction has no role in preventing an allergic reaction.
Anaphylatic reactions should be recognized when patients develop the symptoms described on the previous page. The transfusion must be stopped immediately. Differential diagnosis includes hypotensive reactions, transfusion-related acute lung injury (TRALI), myocardial infarction, and pulmonary embolism. An IgA deficiency should be investigated and is confirmed by the presence of anti-IgA. Treatment includes timely administration of epinephrine in addition to other supportive care such as vasopressors and airway support. Patients with anti-IgA and severe reactions to plasma proteins should only receive washed red cells. Plasma transfusions should be avoided when possible. Products may also be collected from donors who are known to be IgA-deficient, although Ig-A-deficient plasma is rare. Autologous donations are an alternative.