Blood Groups and Blood Transfusion

Question 1

What are red cell antigens ?

Answer 1

Antigens present of the surface of red blood cells. (found in the lipid layer, extracellular)

26 blood group systems

• ABO and Rhesus systems are most important
• Kell, Duffy etc. less likely to cause clinical conditions

Question 2

Describe an antibody-antigen reaction

Answer 2

Antibody produced by B cells in response to non-self antigens presented to T cells by antigen presenting cells - monocytes, macrophages

IgG antibodies mainly after exposure to blood transfusions or foeto-maternal transmission.

Naturally occurring IgM antibodies present at/soon after birth against antigens that the individual lacks.

Question 3

Describe the structure of an antibody

Answer 3

Fab region - antigen binding region

Fc region - fraction crystallisable region

Question 4

State the typical structure of an IgM antibody

Answer 4

Pentamer

Question 5

Feature of IgM antibodies

Answer 5

IgM antibodies are more dangerous than IgG antibodies in immune hemolysis.

Question 6

Describe the action of IgM

Answer 6

IgM antibodies can agglutinate red cells

IgM activates compliment and the membrane attack complex rapidly destroys cells

Question 7

Describe the action of IgG

Answer 7

IgG does not damage circulating red cells.

Fc receptors on splenic macrophages bind IgG-coated red cells, which may then be gradually destroyed.

Question 8

Describe the ABO system

Answer 8

FUT1 and FUT2 genes (on chromosome 19) code for H substance

A and B genes (on chromosome 9) code for glucosyl transferases which add further sugar groups.

Naturally occurring anti-A and/or B IgM antibodies in individuals lacking these antigens

Question 9

H substance

Answer 9

Sugar chain that projects out from the cell surface.

Virtually everyone has H substance

(chromosome 19)

Question 10

Function of A / B genes

Answer 10

Transfer one more sugar group onto the pre-existing chain of sugars (H substance)

(chromosome 9)

Question 11

Group O

Answer 11

Neither A or B antigens

They have naturally occurring anti-A and anti-B antibodies.

Question 12

Describe the A / B antigens location

Answer 12

Transmembrane antigens
Stick out into the plasma

Question 13

Group O
(What antibodies are present ?)

Answer 13

Anti-A
Anti-B
(in plasma)
46% UK

Question 14

Group A
(What antibodies are present ?)

Answer 14

Anti-B
(in plasma)
42% UK

Question 15

Group B
(What antibodies are present ?)

Answer 15

Anti-A
(in plasma)
9% UK

Question 16

Group AB
(What antibodies are present ?)

Answer 16

No naturally occurring antibodies

3% UK

Question 17

Describe ABO grouping on a glass tile

Answer 17

Positive reaction = clumping of cells

Question 18

Blood products examples

Answer 18

Plasma reduced cells

Pooled platelet concentrate

Fresh frozen plasma / cryoprecipitate

Question 19

How is blood grouping carried out ?

Answer 19

Using gel columns
ABO and Rh grouping in micro-titre gel tubes

Positive reaction = cells held high in gel after centrifugation

Question 20

If a person is blood group O, what ABO antibodies would his plasma contain ?

Answer 20

Anti-A and Anti-B

Question 21

A person who is group A will have what characteristics on their red cells and in their plasma ?

Answer 21

A antigens on cells

Anti-B in plasma

Question 22

Describe the Rhesus system

Answer 22

Antigens c C D e E

Coded for on chromosome 1 and inherited as a triplet : e.g. cDe

‘Rhesus negative’ implies D negative

No naturally occurring antibodies but can develop in response to pregnancy or transfusion.

Question 23

Rhesus negative

Answer 23

D negative

Question 24

Difference between ABO and Rhesus system

Answer 24

Rhesus system does not have a naturally occurring antibody against antigens we lack.

We only develop them in response to blood transfusion or pregnancy.

Question 25

What is haemolytic disease of the newborn ?

Answer 25

Foetal red cells carry antigens from the mother and the father (includes Rh antigens). The baby carries an antigen (from the father) that the mother does not have. Foetal red cells carrying antigens from the father, transferring to maternal circulation. Mother recognises these as not her cells, and so can produce antibodies against these.

Question 26

Describe what happens in haemolytic disease of the newborn

Answer 26

Mother produces IgG antibodies in response to (e.g. D, c, E, Kell) Antibodies cross the placenta causing anaemia, jaundice, brain damage or foetal death.

Question 27

Explain how haemolytic disease of the newborn can affect the second pregnancy

Answer 27

In the 1st pregnancy, the Rh- woman has conceived a Rh+ foetus During labour, foetal red cells leak into the mother. The foetal red cells survive long enough to elicit an IgG response. The maternal anti-D antibodies cross the placenta in the 2nd pregnancy and attack foetal red cells.

Question 28

Describe prevention of Rh D reaction

Answer 28

Via immunisation Anti-D prophylaxis offered to D negative mothers @ 28 weeks + delivery + after obstetric events.

Question 29

Function of Kleihauer test

Answer 29

Looks for foetal cells in maternal circulation. Acid elution (washing out) of Hb - foetal Hb is more resistant - looks darker circles (as Hb is not washed out)

Question 30

Describe foetal monitoring

Answer 30

Foetus of mother with significant red cell antibodies can be monitored for anaemia : - flow in middle cerebral artery - ascites - liver and spleen size (getting larger) Umbilical cord sampling for blood count /blood group and antibody level

Question 31

Treatment of Rh D immunisation

Answer 31

Foetal monitoring by ultrasound Can receive intra-uterine transfusion

Question 32

Describe neonatal management

Answer 32

Clinical assessment - Blood count - Phototherapy to increase bilirubin conjugation - Top-up or exchange transfusion

Question 33

Coombes test

Answer 33

Looks for membrane-bound antibody - Allow antibodies to decline - Top-up or exchange transfusion

Question 34

Describe cross-matching blood

Answer 34

Donor blood is checked for ABO, Rh D and other antigens Microbiology screening - HIV, Hep B Recipients blood is checked for ABO and Rh D group. Plasma is screened for antibodies against a panel of red cell antigens. The recipients plasma is mixed with donor red cells to check for agglutination.

Question 35

Why is the recipients plasma mixed with donor red cells ?

Answer 35

To check for agglutination - If there is a reaction the cells will stay at the top of the tube

Question 36

Typical uses plasma reduced cells

Answer 36

Haematological conditions causing under production of blood : - Trauma - GI bleeding - Childbirth - Peri-operative

Question 37

Typical uses for platelets

Answer 37

Marrow failure Massive haemorrhage

Question 38

Typical uses for fresh frozen plasma

Answer 38

Liver failure Massive haemorrhage

Question 39

Blood transfusion consent

Answer 39

Formal signed consent is NOT taken in the UK Leaflet and discussion about: - Risks and benefits - Alternative options ... but emergency use is valid, even if patient cannot give consent

Question 40

Describe transfusion reactions

Answer 40

Acute haemolytic reactions (pre-existing antibodies) usually due to miss-matched blood Delayed haemolytic reactions (new antibodies formed following transfusion) Urticaria or anaphylaxis (drugs or plasma proteins) Febrile reactions (HLA antibodies)

Question 41

Which transfusion reaction is most serious ?

Answer 41

ABO mismatch is MOST serious - Group A individual has less anti-B than a group O individual

Question 42

Management of acute transfusion reaction

Answer 42

Stop the transfusion Assess the patient Return the blood bag, FBC, biochem, blood cultures, 3x transfusion tubes to lab IV fluids Monitor urine output, renal function and coagulation

Question 43

Acute transfusion reaction timings

Answer 43

Most severe reactions are within minutes of starting

Question 44

What to do in the case of a urticarial reaction ?

Answer 44

Temporarily stop blood Gove IV piriton Review 30 minutes Continue transfusion if settling

Question 45

Some symptoms of anaphylaxis

Answer 45

Runny nose Respiratory symptoms Hives, Itchiness Heart symptoms Swelling of tongue, lips etc.

Question 46

Human errors in transfusion

Answer 46

Failure to establish patient identity and/or label tube incorrectly when taking blood Failure to perform bedside check of patient identity when administering blood Lab errors - e.g. incorrect sample used or antibodies not working