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Blood bank — compatibility testing, components and transfusion reactions
Safe transfusion rests on correct identification of patient and sample, on blood group (ABO and RhD) and antibody screening before transfusion, and on rapid recognition of a reaction — the most serious of which, acute haemolytic reaction from ABO incompatibility, is caused in most cases by an identification error rather than a laboratory failure.
Why it matters in the exam
The bank asks about tests, storage and reaction types. In ABO there are naturally occurring IgM antibodies against the missing antigen, so incompatibility causes immediate intravascular haemolysis; O is the "universal" red-cell donor and AB the "universal" plasma donor. RhD antibodies are IgG formed after exposure. "Type and screen" includes ABO, RhD and an antibody screen by indirect Coombs testing, which looks for antibodies in the patient's serum; direct Coombs testing looks for antibodies or complement already on the red cells — in autoimmune haemolytic anaemia, haemolytic disease of the fetus and haemolytic transfusion reaction.
Component storage: red cells at 1–6 degrees for up to 42 days; platelets at room temperature, 20–24 degrees, with agitation, for a few days — so they are the component with the highest risk of bacterial contamination; fresh frozen plasma frozen; and cryoprecipitate rich in fibrinogen, factor VIII, von Willebrand factor and factor XIII. Leukoreduction reduces febrile reactions, CMV transmission and HLA antibody formation; irradiation prevents transfusion-associated GVHD in at-risk patients.
Reactions: acute haemolytic — fever, chills, back pain, hypotension, dark urine and intravascular coagulation — stop the transfusion immediately and check identification; febrile non-haemolytic — from cytokines, the most common; allergic — urticaria; anaphylactic — sometimes in IgA deficiency with anti-IgA antibodies; TRALI — non-cardiogenic pulmonary oedema within 6 hours, from donor HLA or HNA antibodies; TACO — volume overload with hypertension and raised BNP; delayed haemolytic — 3–14 days after transfusion, from an anamnestic response to an antibody such as Kidd.
Key points
- Before transfusion: ABO, RhD and antibody screen.
- Direct Coombs — on the cells; indirect — in the serum.
- Red cells 1–6 degrees up to 42 days; platelets 20–24 degrees.
- Acute haemolytic — usually identification error; stop immediately.
- TRALI within 6 hours; TACO volume overload; delayed 3–14 days.
Summary table
| Component or reaction | Key fact | Time or condition | Pitfall |
|---|---|---|---|
| Red cells | 1–6 degrees | Up to 42 days | — |
| Platelets | 20–24 degrees with agitation | A few days | Highest risk of bacterial contamination |
| Acute haemolytic | ABO incompatibility, usually identification error | Minutes | Continuing the transfusion |
| TRALI versus TACO | Donor antibodies versus volume overload | TRALI within 6 hours | Treating TRALI with diuretics |
| Delayed haemolytic | Anamnestic response, for example Kidd | 3–14 days | Thinking a negative screen excludes forever |
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Sources
- AABB Technical Manual, 21st edition (2023) — Pretransfusion testing; blood components; adverse reactions
- British Society for Haematology: Guidelines on the administration of blood components and pre-transfusion compatibility procedures, 2017–2023 — Identification and testing
- International Society of Blood Transfusion: Haemovigilance definitions of transfusion reactions, 2018 — Definitions of TRALI, TACO and haemolytic reactions
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.