Blood groups and Transfusions Flashcards
1
Q
Red Cell Antigens
A
• Present on surface of red blood cell
2
Q
Antibody-Antigen reaction
A
- IgG antibodies mainly after exposure to blood transfusions or foeto-maternal transmission
- IgM antibodies occur due to components in food which mimic A and B antigens
3
Q
what genes code for the H substance
A
FUT1 and FUT2 genes (chromosome 19)
4
Q
what do A and B genes on chromosome 9 code for
A
glucosyl transferases which add further sugar groups
5
Q
o
A
anti-A, Anti-B 46%
6
Q
a
A
Anti-B 42%
7
Q
b
A
Anti-A 9%
8
Q
ab
A
None 3%
9
Q
Rhesus system
A
- Antigens c C D e E
- coded for on chromosome 1 and inherited as a triplet eg cDe
- ‘Rhesus negative’ implies D negative
- No naturally occurring antibodies but can develop in response to pregnancy or transfusion
10
Q
Haemolytic disease of the newborn
A
- Foetal red cells carrying antigens from the father transferring to maternal circulation
- Mother produces IgG antibodies to eg D, c, E, Kell
- Antibodies cross the placenta causing anaemia, jaundice, brain damage or foetal death
11
Q
Prevention of Rhesus D immunisation
A
- Anti-D prophylaxis given to D negative mothers at 28 weeks and delivery (40 weeks) and after obstetric “events”
- Kleihauer test looks for foetal cells in maternal circulation
12
Q
Foetal monitoring
A
- Foetus of mother with significant red cell antibodies can be monitored for anaemia eg
- Flow in middle cerebral artery Ascites
- Liver and spleen size
- Umbilical cord sampling for blood count/blood group and antibody level
13
Q
Treatment of Rhesus D immunisation
A
- Foetal monitoring by ultrasound
* Can receive intra-uterine transfusion
14
Q
Neonatal management of rhesus negative children
A
- Clinical assessment
- Blood count and reticulocytes/group/red cell antibodies/bilirubin/direct Coombes test looking for membrane-bound antibody
- Allow antibodies to decline
- Phototherapy to increase bilirubin conjugation
- Top-up or exchange transfusion
15
Q
Cross-matching blood
A
- Donor blood is checked for ABO, rhesus D and often other antigens and the bag is labelled. Also microbiology screening- HIV, Hepatitis etc
- Recipient’s blood is checked for ABO and rhesus D group and the plasma screened for antibodies against a panel of red cell antigens
- Recipient’s plasma is mixed with donor red cells to check for agglutination
