Definitions:
Acute haemolytic transfusion reactions (AHTR) are characterised by fever, a fall in haemoglobin (Hb), rise in bilirubin and lactate dehydrogenase (LDH) and a positive direct antiglobulin test (DAT). They generally present within 24 hours of transfusion.
Delayed haemolytic transfusion reactions (DHTR), occur more than 24 hours following a transfusion and are associated with a fall in Hb or failure to increment, rise in bilirubin and LDH and an incompatible crossmatch not detectable pre transfusion.
Hyperhaemolysis (HH) is characterised by more severe haemolysis than DHTR, with haemolysis affecting the transfused red cells and the patient’s own red cells; there is a decrease in Hb to below pre-transfusion levels, which is often associated with a reticulocytopenia. It may be triggered by a new red cell alloantibody, but frequently no new red cell antibody is identified. Hyperhaemolysis can be divided into acute and delayed hyperhaemolysis.
SHOT has collected data on haemolytic transfusion reactions (HTR) since 1996. Until 2006, this category only included delayed HTR, as acute reactions were reported under the ATR category. Alloimmunisations are not included within the numbers in the figure above.
SHOT Transfusion Safety Standards
The SHOT Transfusion Safety Standards were released in July 2025, and these replace recommendations in the Annual SHOT Reports. More details on these can be found at: https://www.shotuk.org/transfusion-safety/transfusion-safety-standards/
Recommendations from recent Annual SHOT Reports (prior to 2024)
Effective communication is vital to maintain transfusion safety, this includes communicating the reasons for, and risks of transfusion to the patient, communication between clinical areas and communication between hospitals
Action: All staff involved in transfusion
Provide as much information as possible to SHOT when reporting, including the investigations performed, treatment modality and patient outcome
Action: Haemovigilance reporters
Do not withhold lifesaving transfusion, even if the patient has a history of alloantibodies, and carefully monitor the patient for signs and symptoms of a haemolytic transfusion reaction
Action: Clinical staff involved in transfusion
Laboratory protocols should include a full investigation for HTR which might include referring samples when resources for testing are not available locally
Action: Laboratory staff involved in transfusion
Please see the individual SHOT chapters below for other previous recommendations which remain relevant.
HTR Resources
SHOT Bite No. 15: Hyperhaemolysis
HTR Annual Report Chapters
To access the chapter click either on the cover of the Annual SHOT Report or the link below the picture
