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transfusion science/Acute transfusion services Flashcards

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1
Q

what is blood?

A

blood is a tissue

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2
Q

what is a blood transfusion?

A

a partial organ/tissue transplant

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3
Q

what do red blood cells carry?

A

antigens

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4
Q

what does blood plasma contain?

A

the antibodies to cell antigens

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5
Q

what does an effective transfusion require?

A

donor and recipient to be typed and ‘cross-matched’ to avoid destruction of the transfused cells

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6
Q

what can a blood transfusion stimulate?

A

an immune response in the recipient

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7
Q

why can a blood transfusion transmit disease?

A

because blood is a biological fluid

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8
Q

what determines blood group specificity?

A

The inherited antigens on red cells

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9
Q

where are blood group antigens found?

A

Carried on the protein components inserted in the red cell membrane

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10
Q

what are blood group antibodies?

A

Proteins produced by an immune response. May be IgG, or IgM antibodies

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11
Q

what is the most important system in transfusion practice?

A

ABO blood group system

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12
Q

what can happen if there is an ABO incompatible transfusion?

A

can cause serious/fatal transfusion reactions

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13
Q

what can ABO antibodies cause?

A

rapid & total destruction of incompatible blood intravascularly

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14
Q

can the ABO antibodies cross the placenta?

A

no

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15
Q

what is Landsteiners theory?

A
  • 2 different antigens (A+B) on surface of blood cells

- identified a group of blood cells with no antigen which he called O for zero

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16
Q

what are the 4 possible blood groups in the ABO system?

A

A
B
AB
O

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17
Q

what are the characteristics of Group A individuals?

A

A antigen on red cells

Anti-B antibody in plasma

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18
Q

what are the characteristics of Group B individuals?

A

B antigen on red cells

Anti-A antibody in plasma

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19
Q

what are the characteristics of blood group AB individuals?

A

A and B antigen on red cells

Neither anti A or anti B antibodies in plasma

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20
Q

what are the characteristics of Group O individuals?

A

No antigens on red cells

Both anti-A and anti B antibodies in plasma

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21
Q

how are the ABO blood groups inherited?

A

One set of genes from mother/one set from father

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22
Q

what are examples of homozygous inheritance of blood group?

A

AA
BB
OO

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23
Q

what are examples of heterozygous inheritance of blood group?

A

AO
BO
AB

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24
Q

which genes are co-dominant in blood group inheritance?

A

A and B genes

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25
if there are AO genes what is the blood group?
Blood group A
26
if there are BO genes what is the blood group?
Blood group B
27
if there are AB genes what is the blood group?
Blood group AB
28
is the O gene recessive or dominant?
recessive
29
how does an individual inherit blood group O?
OO genes
30
how is blood group expression controlled?
by three separate genetic loci
31
what are the three loci that control blood group expression?
ABO on chromosome 9 H on chromosome 19 (FUT1) Se (secretor geen) also on chromosome 19 (FUT2)
32
how are blood group genes inherited?
in pairs of Mendelian dominants
33
what sort of gene is the O gene?
an AMORPH i.e. there is no active gene product
34
what is the H antigen?
a precursor of A and B antigens
35
what antigens are found on blood group O?
H
36
what are the 3 ABO blood group antigens?
A B H
37
what sort of molecules are the blood group antigens?
Oligosaccharides
38
where are ABH antigens expressed?
on most tissues
39
what do 80% of the population possess?
secretor gene
40
where is the secretor gene found?
Secreted in body fluids such as saliva, sweat and semen
41
what determines the subgroups of A and B blood groups?
Variation in the number of A and B antigens on the red cell membrane
42
why are there subgroups of A and B blood groups?
less A and B antigens More H antigen
43
what is the second most important system in transfusion practice?
Rh blood group system
44
what antigen is in the Rh blood group system?
D antigen
45
what are the groups of the Rh blood group system?
Rhesus D positive (RhD positive) Rhesus D negative (RhD negative)
46
what are the 6 alleles in the Rh system?
``` C c D d E e ```
47
are the alleles of the Rh blood group system recessive?
no, all are co- dominant
48
how is the Rh system inherited?
through 2 structurally related genes on chromosome 1 - RhD - RhCE
49
what do the genes on chromosome 1 encode for?
Encode for proteins that carry the antigens C c D E e
50
what is the main antigen that is looked for in transfusion?
D
51
what is the main problem with D antigen?
Haemolytic Disease of the Newborn
52
are Rh antibodies naturally occurring?
No, they are formed through blood transfusion or pregnancy
53
what is the most common antibody of the Rh system?
Anti-D
54
can anti-D antibody cross the placenta?
yes
55
what did the Fishers CDE system determine about the Rh system?
- 3 pairs of closely linked genes | - Allow 8 possible haplotypes
56
what did the Two-Locus model suggest?
2 genes - RhD - RhCE
57
what are the 8 possible haplotypes of Rh system?
``` DCe DcE Dce DCE dCe dcE dCE dce ```
58
what is the fisher nomenclature for the 8 possible haplotypes?
``` DCe - R1 DcE - R2 Dce - R0 DCE - Rz dCe - rʹ dcE - rʺ dCE - ry dce - r ```
59
what causes irregular antibodies to form?
AS A RESULT OF PREGNANCY OR TRANSFUSION NOT NATURALLY OCCURING
60
what is haemolytic disease of the newborn?
An alloimmune condition that develops in the foetus
61
what happens during haemolytic disease of the newborn?
IgG antibodies produced by the mother cross the placenta Attack the red blood cells in the foetal circulation
62
when does haemolytic disease of the newborn occur?
Mother = Rh D negative Father = Rh D positive
63
what can cause haemolytic disease of the newborn?
Transplacental bleed at delivery or pre-natal trauma Mother becomes sensitised by D antigen Mother produces IgG Anti D-able to cross the placenta If next pregnancy is Rh D positive foetus Mothers anti D binds with D antigen on foetal red cells, causing haemolysis of foetal red cells
64
what are the clinical effects of HDNB on the foetus/neonate?
- Hb levels fall- due to haemolysis of Rbc’s - Bilirubin levels raise-breakdown product haemoglobin - Exchange transfusion may be necessary - Brain damage - Intrauterine death from hydrops foetalis
65
what are some tests that can be used to detect antibodies formed by the mother?
``` ABO group Rh group Antibody screen Antibody identification Genotype father Antibody titre throughout pregnancy ```
66
what does the effect of HDNB depend on?
antibody titre
67
what tests can be done on affected foetus?
- amniocentesis - Rh status-chorionic villus sampling (CVS) - PCR testing of mothers blood for foetal DNA - Velocimetry - can transfuse foetus in utero
68
what does amniocentesis do?
estimates antibody levels
69
what is velocimetry?
Use of Doppler ultrasoniography to measure blood flow through foetal cerebral artery
70
what is prophylactic disease prevention?
Stops disease occurring before the event
71
what is the prophylactic disease prevention for HDNB?
Standard dose of Anti D immunoglobulin given to all Rh negative mothers at 28 weeks, and 34 weeks of pregnancy
72
what can be done after delivery to treat HDNB?
baby is Rh positive: - Level of foetal maternal haemorrhage (FMH) assessed using Kleihauer method - 500 IU anti D immunoglobulin administered for each 4 ml FMH - within 72 hours of delivery
73
what are the methods of quantitationof FMH?
Kleihauer- Cheap, simple, not very accurate Flow cytometry/ immunofluorescence- time consuming , expensive, highly accurate. Automated haematology analysers
74
what antibodies can cause HDNB?
``` ABO antibodies-IgG (immune) Anti-C Anti-c Anti-E Anti-e Anti-K Anti-Fya ```
75
what laboratory testing is done in blood transfusion?
- determine recipients ABO and RhD groups | - Perform antibody screenings - identifying presence of irregular antibodies
76
what happens if blood comes up negative for irregular antibodies?
- Choose units of the same group if possible - Add donor RBC’s to recipients plasma - Incubate at 37 degrees - Look for agglutination If non seen issue donor red cells as compatible
77
what happens if antibody screening indicates presence of irregular antibodies?
- Identify antibody - Crossmatch antigen negative blood - - Anti D select D negative donor red cells - - Anti K select Kell negative donor red cells - - Anti Fya select Fya negative donor red cells
78
what is haemoglutination?
clumping together of red blood cells
79
when is an antibody screen done?
on all new patient samples
80
how is the antibody screen done?
- Add patients plasma to the screening cells - Incubate - Observe for agglutination - Record results - Interpret results
81
when is antibody identification carried out?
when antibody screen is positive
82
how is antibody identification done?
- Add patient plasma to panel red cells - Incubate - Observe for agglutination - Record results - Interpret results
83
how do you cross-match patient plasma against antigen negative donor red cell?
- Anti C detected –C antigen negative - Anti D detected – D antigen negative - Anti K detected – K antigen negative - Anti Fya detected- Fya antigen negative
84
what happens if no agglutination is seen after cross-match?
Issue the donor units as compatible.

Haematology (7 decks)

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