Transfusion

Question 1

What is agglutination?

Answer 1

Antibodies bind to RBCs (antigens) which causes visible clumping

Question 2

Direct antiglobin test/ direct Coombs test

Answer 2

Detects antibodies or complement bound to RBCs in vivo.
Used in transfusion reactions and haemolytic anaemia

Question 3

Indirect antiglobulin test / Coombs test

Answer 3

Detects free antibodies in plasma that could attach donor RBCs

Question 4

What is indirect antiglobin/ Coombs test used for?

Answer 4

Antibody screening
Cross matching

Question 5

What is enzyme enhancement?

Answer 5

Proteolytic enzymes eg ficin
Remove sialic acid
Reduce hydration shell
Enhance antibody binding

Question 6

What is the column agglutination test?

Answer 6

Gel matrix separates agglutinated vs non agglutinated cells

Question 7

What is the column agglutination test used for?

Answer 7

ABO grouping
Antibody screening
Cross matching
DAT
New born testing

Question 8

Causes of transfusion reactions in vivo

Answer 8

Haemolytic transfusion reaction

Delayed haemolytic reaction

Febrile non haemolytic reaction

Transfusion related acute lung injury

Transfusion associated circulatory overload

Allergic reaction

Post transfusion purpura

Question 9

Haemolytic transfusion reaction

Answer 9

Recipient antibodies attack donor RBC antigens

Causes complement activation

This triggers intravascular haemolysis

Free haemoglobin causes kidney damage and cytokine storm

Question 10

Delayed haemolytic reaction

Answer 10

Occurs days later
Due to low level antibodies from past transfusions/pregnancies

Question 11

Febrile non haemolytic reaction

Answer 11

Donor white cell cytokines cause fever + chills
No haemolysis

Question 12

Transfusion related acute lung injury

Answer 12

Donor anti HLA antibodies attack patient white cells
Lung endothelial damage
causes acute hypoxia

Question 13

Transfusion associated circulatory overload.

Answer 13

Fluid overload causes pulmonary oedema
Common in Leary failure

Question 14

Allergic reaction

Answer 14

Donor allergens react with recipient IgE
Histamine is released

Question 15

Post transfusion purpura

Answer 15

Recipient lacks HPA-1a
Forms anti HPA 1a which destroys donor and self platelets

Question 16

How to investigate transfusion reactions? - steps

Answer 16

Repeat ABO/RhD typing

Direct antiglobulin test

Check for Haemoglobinuria

Antibody screen and cross match

Blood cultures - rules out bacterial contamination
Clerical check

Question 17

consequences of errors in transfusion

Answer 17

Wrong blood to wrong patient
Haemolytic reaction
Delayed treatment
Organ damage
Death

Question 18

Measures to prevent transfusion errors

Answer 18

Identity checks
Bring antibody cards
Discuss medications
Strict labelling and traceability
Communications between clinical team and lab

Question 19

Definition of massive blood loss

Answer 19

Loss of one blood volume within 24 hours
Or
50% blood loss within 3 hours
Or
150ml/min bleeding rate