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Haematology > transfusion science/Acute transfusion services > Flashcards

transfusion science/Acute transfusion services Flashcards

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
Q

if there are AO genes what is the blood group?

A

Blood group A

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26
Q

if there are BO genes what is the blood group?

A

Blood group B

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27
Q

if there are AB genes what is the blood group?

A

Blood group AB

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28
Q

is the O gene recessive or dominant?

A

recessive

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29
Q

how does an individual inherit blood group O?

A

OO genes

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30
Q

how is blood group expression controlled?

A

by three separate genetic loci

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31
Q

what are the three loci that control blood group expression?

A

ABO on chromosome 9

H on chromosome 19 (FUT1)

Se (secretor geen) also on chromosome 19 (FUT2)

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32
Q

how are blood group genes inherited?

A

in pairs of Mendelian dominants

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33
Q

what sort of gene is the O gene?

A

an AMORPH i.e. there is no active gene product

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34
Q

what is the H antigen?

A

a precursor of A and B antigens

35
Q

what antigens are found on blood group O?

A

H

36
Q

what are the 3 ABO blood group antigens?

A

A
B
H

37
Q

what sort of molecules are the blood group antigens?

A

Oligosaccharides

38
Q

where are ABH antigens expressed?

A

on most tissues

39
Q

what do 80% of the population possess?

A

secretor gene

40
Q

where is the secretor gene found?

A

Secreted in body fluids such as saliva, sweat and semen

41
Q

what determines the subgroups of A and B blood groups?

A

Variation in the number of A and B antigens on the red cell membrane

42
Q

why are there subgroups of A and B blood groups?

A

less A and B antigens

More H antigen

43
Q

what is the second most important system in transfusion practice?

A

Rh blood group system

44
Q

what antigen is in the Rh blood group system?

A

D antigen

45
Q

what are the groups of the Rh blood group system?

A

Rhesus D positive (RhD positive)

Rhesus D negative (RhD negative)

46
Q

what are the 6 alleles in the Rh system?

A 
C
c
D
d
E
e
47
Q

are the alleles of the Rh blood group system recessive?

A

no, all are co- dominant

48
Q

how is the Rh system inherited?

A

through 2 structurally related genes on chromosome 1

  • RhD
  • RhCE
49
Q

what do the genes on chromosome 1 encode for?

A

Encode for proteins that carry the antigens
C c
D
E e

50
Q

what is the main antigen that is looked for in transfusion?

A

D

51
Q

what is the main problem with D antigen?

A

Haemolytic Disease of the Newborn

52
Q

are Rh antibodies naturally occurring?

A

No, they are formed through blood transfusion or pregnancy

53
Q

what is the most common antibody of the Rh system?

A

Anti-D

54
Q

can anti-D antibody cross the placenta?

A

yes

55
Q

what did the Fishers CDE system determine about the Rh system?

A
  • 3 pairs of closely linked genes

- Allow 8 possible haplotypes

56
Q

what did the Two-Locus model suggest?

A

2 genes

  • RhD
  • RhCE
57
Q

what are the 8 possible haplotypes of Rh system?

A 
DCe
DcE
Dce
DCE
dCe
dcE
dCE
dce
58
Q

what is the fisher nomenclature for the 8 possible haplotypes?

A 
DCe -	R1		
DcE -	R2		
Dce -	R0		
DCE -	Rz
dCe -	rʹ
dcE -	rʺ
dCE -	ry
dce -	r
59
Q

what causes irregular antibodies to form?

A

AS A RESULT OF PREGNANCY OR TRANSFUSION

NOT NATURALLY OCCURING

60
Q

what is haemolytic disease of the newborn?

A

An alloimmune condition that develops in the foetus

61
Q

what happens during haemolytic disease of the newborn?

A

IgG antibodies produced by the mother cross the placenta

Attack the red blood cells in the foetal circulation

62
Q

when does haemolytic disease of the newborn occur?

A

Mother = Rh D negative

Father = Rh D positive

63
Q

what can cause haemolytic disease of the newborn?

A

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
Q

what are the clinical effects of HDNB on the foetus/neonate?

A
  • 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
Q

what are some tests that can be used to detect antibodies formed by the mother?

A 
ABO group
Rh group
Antibody screen
Antibody identification
Genotype father
Antibody titre throughout pregnancy
66
Q

what does the effect of HDNB depend on?

A

antibody titre

67
Q

what tests can be done on affected foetus?

A
  • amniocentesis
  • Rh status-chorionic villus sampling (CVS)
  • PCR testing of mothers blood for foetal DNA
  • Velocimetry
  • can transfuse foetus in utero
68
Q

what does amniocentesis do?

A

estimates antibody levels

69
Q

what is velocimetry?

A

Use of Doppler ultrasoniography to measure blood flow through foetal cerebral artery

70
Q

what is prophylactic disease prevention?

A

Stops disease occurring before the event

71
Q

what is the prophylactic disease prevention for HDNB?

A

Standard dose of Anti D immunoglobulin given to all Rh negative mothers at 28 weeks, and 34 weeks of pregnancy

72
Q

what can be done after delivery to treat HDNB?

A

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
Q

what are the methods of quantitationof FMH?

A

Kleihauer- Cheap, simple, not very accurate

Flow cytometry/ immunofluorescence- time consuming , expensive, highly accurate.

Automated haematology analysers

74
Q

what antibodies can cause HDNB?

A 
ABO antibodies-IgG (immune)
Anti-C
Anti-c
Anti-E
Anti-e
Anti-K
Anti-Fya
75
Q

what laboratory testing is done in blood transfusion?

A
  • determine recipients ABO and RhD groups

- Perform antibody screenings - identifying presence of irregular antibodies

76
Q

what happens if blood comes up negative for irregular antibodies?

A
  • 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
Q

what happens if antibody screening indicates presence of irregular antibodies?

A
  • 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
Q

what is haemoglutination?

A

clumping together of red blood cells

79
Q

when is an antibody screen done?

A

on all new patient samples

80
Q

how is the antibody screen done?

A
  • Add patients plasma to the screening cells
  • Incubate
  • Observe for agglutination
  • Record results
  • Interpret results
81
Q

when is antibody identification carried out?

A

when antibody screen is positive

82
Q

how is antibody identification done?

A
  • Add patient plasma to panel red cells
  • Incubate
  • Observe for agglutination
  • Record results
  • Interpret results
83
Q

how do you cross-match patient plasma against antigen negative donor red cell?

A
  • 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
Q

what happens if no agglutination is seen after cross-match?

A

Issue the donor units as compatible.

Haematology (7 decks)

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