Investigation - Anaphylactic Transfusion Reactions

If a patient develops an anaphylactic or severe anaphylactoid transfusion reaction the patient’s pretransfusion serum must be screened for the presence of anti-IgA. Screening tests for IgA deficiency are available in many hospital laboratories. Anti-IgA usually occurs only in the presence of IgA deficiency. However it may also occur in the presence of a sub-class deficiency.

Patients without detectable IgA in screening tests (or if the test is unavailable), or patients who have experienced more than one anaphylactoid reaction should have specimens referred to Canadian Blood Services.

• If IgA antibodies are present, the patient is a candidate for IgA-deficient blood components
• If anti-IgA antibodies are absent, the patient should also be tested for haptoglobin deficiency, since anaphylactoid reactions due to this deficiency have also been described. Otherwise, no further laboratory testing is usually done.

It is important to differentiate anaphylactic/anaphylactoid transfusion reactions from other transfusion reactions such as immediate hemolytic transfusion reactions, circulatory overload, bacterial sepsis and TRALI, which may present similar signs and symptoms. It is also important to consider than an anaphylactic/anaphylactoid reaction may result from medical treatment other than blood transfusions.

Instructions for sending samples for IgA/anti-IgA testing:

1. Collect at least 2 mL of serum or plasma.
2. Forward sample and patient information to local CBS site.
3. Patient information includes:

• Full name
• Date of birth
• Sample collection date
• Originating lab contact information
• Identification number
• Pertinent transfusion history
• Reason for request