Blood Groups & Transfusion

Question 1

What forms blood groups?

Answer 1

Lipid bilayer with sugar residues and proteins on RBC surface
Sugar residues form type of blood group - ABO
Proteins form another type of blood group - rhesus
Genes determine what sugar and protein in produced and therefore the blood group

Question 2

What are antigens?

Answer 2

over 300 - some less clinically important

RBC antigens stimulate antibody formation

Question 3

What are antibodies?

Answer 3

• Immunoglobulins in plasma which react specifically with an antigen
• autoantibodies react with antigens on person’s own RBCs
• alloantibodies produced by person against antigens which are not on own RBCs, either naturally occur in environment or part of an immune response

Question 4

What does an antigen-antibody reaction result in?

Answer 4

Agglutination

Question 5

What are the ABO blood groups?

Answer 5

A - has anti-b in plasma
B - has anti-a in plasma
O - has anti a and anti-b in plasma
AB - has no ABO antibody in plasma

Question 6

What does having an anti-a in plasma mean?

Answer 6

Will be agglutinated by anti -a so will form an antigen-antibody reaction.

Question 7

What is a phenotype and genotype?

Answer 7

Phenotype - antigens detectable on RBC membrane

Genotype - antigens encoded in the DNA, 1 copy from each parent

Question 8

What are the phenotypes and genotypes for the blood groups?

Answer 8

Phenotype - A, B, AB, O

Genotype - AA AO, BB, BO, AB, OO

Question 9

What are the relative blood group frequencies?

Answer 9

Most common is O, then A, then B, then AB

Question 10

How do blood groups differ between ethnicities?

Answer 10

Africans - More O, A slightly more than B
European - more A than O
Asian - A and B same, slightly more AB then other ethnicities

Question 11

Which antibodies are naturally occurring?

Answer 11

Anti-a and anti-b

Question 12

Which blood groups can receive and donate from which other group and why?

Answer 12

Blood group A has A antigens with anti-B antibodies and therefore if they receive from B or AB which have B antigens the anti-B antibody would attack it meaning they can only receive from A and O. They can donate to AB and A only.
B type has anti-A antibodies so can only receive from B and O not A and AB. Can donate to B and AB.
AB has no antibodies so can receive from all groups. Can only donate to AB.
O has A and B antibodies so can only receive from O. Can donate to all.

Question 13

Which is the universal recipient and donor?

Answer 13

AB is universal recipient as no antibodies.

O is universal donor as no antigens.

Question 14

What is the rhesus blood group system?

Answer 14

3 pairs of proteins inherited as a triplet - D, C, E
Inherit one triplet from each parent
Alleles c and e are co-dominant

Question 15

Which alleles are co-dominant?

Answer 15

A and B

C and E

Question 16

What are the phenotypes for Rhesus blood group?

Answer 16

RhD positive - CcDDEe - CcDEe
RhD negative - Ccddee - Ccde
RhD negative - ccddee - cde
(rhesus negative has lower case d)

Question 17

How do you determine the phenotype for rhesus system?

Answer 17

• serologically
• put RBCs into wells each coated with one antibody and if antigen is present it will agglutinate with antibody and will not sink to the bottom so C/c/D/d/E/e positive or negative can be determined

Question 18

What are the approximate frequencies for Rhesus blood group?

Answer 18

More rhesus positive across all ethnicities by a significant amount

Question 19

What blood should rhesus positive and negative individuals receive?

Answer 19

Rhesus positive - rhesus positive or negative

Rhesus negative - rhesus negative, avoid positive

Question 20

How can a haemolytic disease and the foetus and newborn develop?

Answer 20

Rhesus positive father and rhesus negative mother produce a rhesus positive foetus
Rhesus negative mother carries positive fetus and during delivery blood can enter mother’s
Mother will produce anti-Rh antibodies in response to fetal antigens
During next pregnancy anti-Rh antibodies will cross placenta to Rhesus positive foetus and damage fetal RBCs
This all results in foetal anaemia and/or neonatal jaundice

Question 21

What are some ways to manage a haemolytic disease developing in the foetus/newborn?

Answer 21

Prophylaxis anti-D Ig the all negative mothers in third trimester

Question 22

What are some good clinical practice methods to avoid haemolytic disease?

Answer 22

Monitor adverse reactions
Patient identification
Sample labelling
Laboratory testing

Question 23

How are RBCs stored?

Answer 23

At 4 degrees, 35 day shelf life

Question 24

What are some indications for blood transfusion?

Answer 24

Blood loss - surgery, trauma, obstetric haemorrhage
Bone marrow failure - leukaemia, cancer, drugs
Haemolysis - malaria, sepsis, haemolytic disease of newborn
Inherited haemoglobin disorders - SC anaemia, thalassaemia
Anaemia due to iron, B12, folate deficiency - try and avoid transfusion and give haematinic replacement therapy instead

Question 25

What are some complications of transfusion?

Answer 25

Infectious - viral (HIV, HepE, HBV), bacterial, syphilis, parasites (malaria) Non infectious - acute haemolytic transfusion reaction, delayed haemolytic transfusion reaction, allergic urticarial rash, transfusion related lung injury Non immune - fluid overload, iron overload

Question 26

What are the most common reasons for ABO incompatibility?

Answer 26

Patient wrongly identified - unconscious, no wristband, human error, pre-transfusion sample from wrong patient

Question 27

What is an indirect antiglobulin test?

Answer 27

Used to detect IgG - alloantibodies formed after previous pregnancy or transfusion - patients serum (containing IgG), incubate with reagent RBCs that will bind to IgG, incubate with antibodies to Ig, will agglutinate (positive indirect Coombs test)

Question 28

What should be monitored during a transfusion?

Answer 28

before - confirm patient identity, blood group, blood group of unit of blood Pulse, bp, temperature

Question 29

How does a transfusion reaction present?

Answer 29

Signs - fever, hypotension, haemoglobinuria Symptoms - restless, flushing, anxiety, abdominal pain, nausea, diarrhoea, pain at venupuncture site STOP TRANSFUSION AND MAINTAIN VENOUS ACCESS WITH SALINE

Question 30

What types of antibodies are anti-a and b?

Answer 30

IgG and IgM

Question 31

What laboratory tests are done?

Answer 31

1 - Indirect positive coombes test where you mix all of patients plasma (containing antibodies) with blood type O (no antigens) mixed with all antigens to then see which ones agglutinate 2- Electronic crossmatching - check for any antibodies - if none then must be AB rhesus negative so can receive from all blood types 3 - serological crossmatching - if antibodies are present mix donor RBCs and patients plasma to check antibodies then do rhesus test with wells

Question 32

What is the indirect Coombes test?

Answer 32

Tests for autoimmune haemolytic anaemia where IgG antibodies attack RBC membrane proteins

Question 33

What can the effects of autoimmune haemolytic anaemia be?

Answer 33

jaundice | failure of haemoglobin to rise

Question 34

What can blood transfusions be used for?

Answer 34

``` blood loss - trauma, surgery, haemorrhage bone marrow failure - leukaemia haemolysis - malaria, sepsis inherited haemoglobin disorders anaemia ```

Question 35

How do you investigate a transfusion reaction?

Answer 35

Take samples for FBC, renal and liver function tests, blood culutres, coagulation screen Repeat compatibility testing pre and post transfusion Direct antiglobulin test Assess urine for haemoglobin High dependency management - Renal support

Question 36

What is the difference between the direct and indirect Coombes test?

Answer 36

Direct - RBCs are already attached to IgG and get mixed with IgG antibodies to confirm attack on own RBCs Indirect - use RBCs which are not attached to IgG and mix with IgG antibodies to see if IgG are present