Haematology and Immunology - ABO grouping & transfusion

Question 1

Explain the blood grouping systems

Answer 1

ABO
Groups A&B have IgM antibodies & associated antigens - can precipitate severe haemolytic reactions

Group O (47%) - universal donor, but antibodies against A & B
Group A (42%) can receive A & O, but will react to B or AB
Group B (8%) can receive B & O, but will react to A or AB
Group AB (3%) universal recipient, no antibodies

Rhesus (Rh)
Second most commonly used classification system
Antigen D is +ve or -ve on surface of RBC
Approx 85% of UK population are Rh+, determined by 2 loci on chromosome 1

Antibodies generated when Rh-ve patient exposed to Rh+, for example transfusion, or Rh+ve baby to Rh-ve mother
This sensitises the patient, and antibodies will be present for the next exposure, causing haemolytic disease of the newborn (Rh-ve mothers offered anti-D immunoglobulin to reduce chance of antibody formation)

Other minor groups (Duffy, Lewis, Kidd & Kell) may be responsible for less severe reactions, or after multiple transfusions

Question 2

Explain the potential complications of blood transfusions

Answer 2

Immunological
Immediate haemolytic transfusion reactions (ABO incompatibility)
Delayed haemolysis at 7-10 days (minor group incompatibility)
Febrile non-haemolytic transfusion reaction
Transfusion related lung injury (TRALI)
Haemorrhagic disease of the newborn

Infective
Donors excluded if risk of hepatitis, HIV, malaria, syphilis, brucellosis
Bacterial contamination by gram -ve organisms can lead to septic shock
Creutzfeld-Jakob disease (blood now routinely leucodepleted)

Cardiovascular
Cardiac failure (TACO - Transfusion associated cardiac overload)
Left shift of oxygen dissociation curve
Coagulopathy
Thromboembolism & phlebitis

Metabolic
Hyperkalaemia, hypocalcaemia & citrate overdose, acidosis, iron overload, hypothermia