Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
Delayed transfusion reactions and alloimmunisation
Essential points for quick revision.
2 min synopsisUK scopeSources checked 27 Aug 2026Clinical review pending
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Hyperhaemolysis or suspected TA-GVHD
Haemoglobin below the pretransfusion baseline with reticulocytopenia, or fever, rash, diarrhoea and pancytopenia one to two weeks after transfusion, requires urgent specialist management.
Action: Contact haematology and the transfusion laboratory immediately, assess ABCDE and send urgent full blood count, reticulocytes, film, bilirubin, LDH, haptoglobin, DAT, repeat antibody testing, renal profile and compatibility samples. In suspected hyperhaemolysis avoid further transfusion unless anaemia is life threatening because additional antigen exposure can accelerate destruction; obtain consultant-led antigen-matched support and immunomodulation. For suspected TA-GVHD isolate and treat sepsis risk, involve transplant or cellular-therapy expertise and notify haemovigilance urgently.
Synopsis
Recognise post-transfusion haemolysis and other delayed complications, investigate new antibodies, prevent re-exposure and distinguish hyperhaemolysis, purpura and graft-versus-host disease.
Delayed haemolytic transfusion reaction occurs more than 24 hours after transfusion, usually within days to several weeks, with haemolysis and a new or re-emergent red-cell antibody.
Key clues are failure of the expected haemoglobin increment, a later haemoglobin fall, jaundice, dark urine, fever, pain, bilirubin or LDH rise, low haptoglobin and a new positive DAT.
Confirmatory assessment combines repeat antibody screen and identification, DAT and eluate where appropriate, repeat crossmatch and antigen typing of patient and implicated units.
Key red flags
A haemoglobin fall below the pretransfusion value with pain, haemoglobinuria or reticulocytopenia suggests hyperhaemolysis, particularly in sickle-cell disease.
Investigation priorities
01
First-line: full blood count and reticulocytesFirst stepFirst line
Measure red-cell or platelet loss and marrow response.
02
First-line: haemolysis screenFirst line
Confirm accelerated red-cell destruction and organ effect.
Management branches
Suspected delayed haemolysisConfirm destruction and preserve compatibility
Haemoglobin falls or jaundice develops more than 24 hours after transfusion.
Send FBC, reticulocytes, bilirubin, LDH, haptoglobin, renal profile, urine and a new compatibility sample and call the transfusion laboratory.
Repeat antibody identification, DAT and retrospective compatibility work, retrieving external and historical antibody records.
Key medicines
Intravenous immunoglobulin for post-transfusion purpuraGive a total of 1 to 2 g/kg intravenously in divided doses over 2 to 5 days under a consultant haematology and transfusion protocol; use the dosing weight required by the commissioned immunoglobulin policy.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.