Classification & incidence of adverse events

Each blood product transfused carries a small risk of an adverse effect.

Fever, chills and urticaria are the most common manifestations of transfusion reactions.

Potentially significant and life-threatening reactions include acute and delayed haemolytic transfusion reactions, transfusion-transmitted bacterial infection (TTBI), anaphylaxis and transfusion-related acute lung injury (TRALI).

It is important to recognise, respond to and report adverse events.

Once you recognise an adverse reaction, follow the steps for managing suspected transfusion reactions.

Classification of Transfusion-related Adverse Reactions and Estimated Incidence

Adverse event Incidence*
Acute haemolytic transfusion reaction (AHTR) 1:76 000b
Fatal acute haemolytic reaction 1:1.8 millionb
Febrile non-haemolytic transfusion reaction (FNHTR) 0.1%–1% of transfusions with universal leucocyte depletionb
Mild allergic reactions (urticarial) 1%–3% of transfusionsb
Severe allergic reactions (anaphylaxis) 1:20 000–1:50 000b
Transfusion-related acute lung injury (TRALI) 1:1200–1:190 000b
Adverse event Incidence*
Complications of massive transfusion Variableb,c
Non-immune mediated haemolysis (physical or chemical destruction of blood) Rarec
Transfusion transmitted bacterial infection (for clinically apparent reactions) due to platelets Approximately 1:250 000a
Transfusion transmitted bacterial infection (for clinically apparent reactions) due to red cells Approximately 1:2.5 milliona
Transfusion-associated circulatory overload (TACO) Up to 1:100 of transfused patientsb
Adverse event Incidence*
Iron overload requiring chelation therapy May occur after 10–20 RBC unitsd
Iron overload with organ dysfunction May occur after 50-100 RBC unitsb
Transfusion-transmissible infections For incidence rates refer to risk estimates for transfusion-transmissible infections

     Note: *Includes overseas data. Risks per unit transfused unless specified.


a. Thyer J, Perkowska-Guse Z, Ismay SL, Keller AJ, Chan HT, Dennington PM, et al. Bacterial testing of platelets - has it prevented transfusion-transmitted bacterial infections in Australia? Vox Sang 2018; 113: 13-20.

b. Savage WJ, Hod EA. Non-infectious complications of blood transfusion. Chapter 22, AABB Technical Manual. 19th edition. AABB, Bethesda, 2017.

c. Popovsky M (ed). Transfusion reactions, 4th edition. AABB Press, Bethesda, 2012.

d. Brittenham GM. Iron-chelating therapy for transfusional iron overload. New England Journal of Medicine 2011 Jan 13;364(2):146–156.