Overview
An allergic transfusion reaction is a cutaneous hypersensitivity reaction, typically urticaria and pruritus, occurring during or shortly after transfusion, attributed to recipient reactivity to donor plasma proteins. It is classified as routine (mild) when confined to cutaneous features with no systemic involvement, after confirming there is no clerical error or hemolysis ambiguity.
Classification
| Feature | Routine allergic reaction | Escalate toward anaphylaxis pathway |
|---|---|---|
| Cutaneous symptoms | Urticaria, pruritus | May also be present |
| Respiratory symptoms | Absent | Present (wheeze, stridor, dyspnea) |
| Hemodynamic status | Stable | Hypotension |
Morphologic Features
Not a cell-morphology topic, this is a reaction-review and documentation reference.
Laboratory Characteristics
- Confirm no clerical error; perform hemolysis-exclusion steps if any diagnostic ambiguity exists
- Document the implicated component type and plasma content (FFP, platelets, cryoprecipitate carry higher allergic association than red cells)
- Review and document prior allergic/transfusion reaction history
- Record precise severity, cutaneous-only vs. any systemic feature
Reference Intervals
Not applicable, qualitative reaction-classification pathway. Institutional criteria for resuming a paused transfusion after symptom resolution are SOP-specific; verify against current protocol.
Clinical and Laboratory Significance
There is no specific confirmatory laboratory test for a mild allergic transfusion reaction; the laboratory's contribution is accurate exclusion of hemolysis, documentation of component/history context, and precise severity assessment that supports correct classification and future product-selection discussions.
Differential Considerations
Distinguish routine allergic transfusion reaction from anaphylactic transfusion reaction (systemic features present), from febrile non-hemolytic reaction (fever-predominant, not urticarial), and from acute hemolytic transfusion reaction (clerical error, hemoglobinemia, positive DAT).
Comparison Tables
Component plasma content and allergic-reaction association
| Component type | Relative allergic-reaction association |
|---|---|
| Fresh frozen plasma | Higher, plasma-rich |
| Platelet concentrate | Higher, plasma-suspended |
| Cryoprecipitate | Higher, plasma-derived |
| Packed/washed red cells | Lower, plasma-poor, especially if washed |
Classification Frameworks
Not applicable, laboratory reaction-classification pathway, not a WHO disease classification.
Laboratory Notes
- Confirm no clerical error before defaulting to an allergic classification
- Document severity precisely, this is what distinguishes routine allergic reaction from anaphylaxis
- Plasma content and prior-history review are documentation tasks, not treatment decisions
References
Authoritative textbooks, guidelines, and reviews supporting this reference entry. Verify reference intervals, critical limits, and reflex criteria against institutional protocols and current guideline editions.
Textbooks
- Cohn CS, Delaney M, Johnson ST, Katz LM, eds. Technical Manual. 21st ed. AABB; 2023.
- Harmening DM. Modern Blood Banking & Transfusion Practices. 7th ed. F.A. Davis; 2019.
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021.
CLSI and Professional Guidelines
- AABB. Standards for Blood Banks and Transfusion Services (verify current edition and institutional adoption).
- World Health Organization. Blood safety and availability / transfusion guidance (verify current WHO publication and institutional adoption).
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