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Haematology > The blood transfusion laboratory > Flashcards

The blood transfusion laboratory Flashcards

1
Q

What are antigens a part of?

A

Antigens are part of the surface of cells

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2
Q

What are antibodies?

A

Antibodies are protein molecules(Igs)

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3
Q

What classes are antibodies usually of?

A

Usually of the Ig classes: IgG and IgM

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4
Q

Where are antibodies found?

A

Found in plasma

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5
Q

What are antibodies produced by and following what?

A

Produced by the immune system following exposure to a foreign antigen

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6
Q

How many blood groups systems are known?

A

There are 26 known blood group systems

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7
Q

What are clinically the most important blood group systems?

A

ABO and Rh are clinically most important

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8
Q

What can antigens in transfused blood stimulate but only under what circumstance?

A

Antigens in transfused blood can stimulate a patient to produce an antibody but only if the patient lacks the antigen themselves

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9
Q

What can stimulate antibody production?

A
  • Blood transfusion
  • Pregnancy
    • Fetal antigens entering maternal circulation during pregnancy or birth
  • Environmental factors
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10
Q

What does an antibody antigen reaction in vivo lead to?

A

Leads to destruction of the cell

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11
Q

What are the 2 ways the cell can undergo destruction when an antibody and antigen react?

A
  • Directly

- Indirectly

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12
Q

Direct destruction of cell

A
  • Directly when the cell breaks up in the blood stream (intravascular)
    • Antibodies and antigens interact to cause haemolysis
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13
Q

Indirect destruction of cell

A

Indirectly when liver and spleen remove antibody coated cells (extravascular)

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14
Q

What does antibody antigen reaction in vitro lead to?

A

Reactions are normally seen as agglutination tests

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15
Q

What is agglutination?

A

Agglutination is the clumping together of red cells into visible agglutinates by antigen-antibody reactions

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16
Q

What does agglutination result from?

A

Agglutination results from antibody cross-linking with the antigens

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17
Q

What can agglutination identify?

A
  • Presence of a red cell antigen

- The presence of an antibody in plasma

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18
Q

What is the clinical significance of the ABO grouping system?

A
  • A and B antigens very common (55% UK)
  • Anti-A, anti-B or anti-A,B antibodies very common (97% UK)
  • High risk of A or B cells being transfused into someone with the antibody in a random situation
  • ABO antibodies can activate complement causing intravascular haemolysis
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19
Q

Steps involved in blood grouping

A
  • The patient’s red cells and plasma are both tested
  • Test patient’s red cells with anti-A, anti-B and anti-D
    - Agglutination shows that a particular antigen is on the red cells
    - No agglutination shows the antigen is absent

Test patient’s plasma with A cells and B cells

      - Agglutination shows that a particular antibody is in the plasma or serum 
      - No agglutination shows the antibody is absent
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20
Q

What is the most important antigen in the RH grouping system?

A

Most important antigen is called D.

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21
Q

What are people with D antigen in terms of RHD?

A

People with D antigen are RhD positive

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22
Q

What are people who don’t produce D antigen in terms of RHD?

A

People who do not produce any D antigen are RhD negative (15%)

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23
Q

What are the other 4 main antigens in the RH grouping system known as, other than D?

A

The other 4 main Rh antigens are known as C, c, E and e

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24
Q

How must RH D typing be tested?

A

Must be tested in duplicate (or tested each time and compared to historical result)

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25
Q

Clinical significance of RH antibodies in transfusion?

A

Transfusion

  • D antigen is very immunogenic and anti-D is easily stimulated - PREVENTION!
  • All Rh antibodies are capable of causing severe transfusion reaction- ANTIBODY DETECTION
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26
Q

Clinical significance of RH antibodies in pregnancy

A
  • Rh antibodies are usually IgG and can cause haemolytic disease of the newborn.
  • Anti-D is still most common cause of severe HDN
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27
Q

What happens in the haemolytic disease of the new born(HDN)?

A
  1. We have a RH+ father
  2. RH- mother is carrying her first RH+ fetus. RH antigens from the developing fetus can enter the mother’s blood during delivery
  3. In response to the fetal RH antigens, the mother produces anti RH antibodies
  4. If the woman with becomes pregnant with another RH+ fetus her anti RH antibodies will cross the placenta and damage fetal red blood cells
28
Q

Why do we screen blood groups and antibodies at antenatal booking?

A

Blood group and antibody screen at antenatal booking to identify pregnancies at risk of HDN

29
Q

At what week do we carry out blood group and antibody screening

A

Blood group and antibody screen at 28 weeks

30
Q

Why are atypical antibodies quantified periodically?

A

Atypical antibodies are quantified periodically to assess their potential effect on the fetus

31
Q

What is RAADP and what does it do?

A

An injection of anti-D and will bind to and remove any fetal RhD positive red cells in the circulation

32
Q

What are RBCs unable to do when bound to anti-D?

A

If red cells bound, they wont be able to stimulate mothers immune system

33
Q

Dosage of anti D

A

1500 iu of anti-D is given routinely at 28 weeks and a smaller dose

34
Q

What events is anti-D also given after?

A

Anti-D is also given after any event that may cause a feto-maternal haemorrhage (bleed between mum and fetus) such as:

  • Abdominal trauma
  • Intrauterine death
  • Spontaneous or therapeutic abortion
35
Q

What is reverse grouping of blood?

A

Looks for corresponding antibodies for the antigens in the plasma

36
Q

Steps involved in reverse grouping of blood

A

1.Patients serum is mixed with 3 selected screening cells

  • Screening cells that have on them the relevant antigen that would cause a problem if a transfusion was given blind
    2. Incubated for 15 minutes at 37c
    3. Centrifuged for 5 minutes
    4. Any clinically significant antibodies reacting at body temp should be detected and then identified using panel of known phenotyped red cells
    5. Specific antigen negative blood can then be provided for these patients to avoid stimulating an immune response
37
Q

What must we do if antibody is detected in reverse grouping of blood?

A
  • Identify the antibody
  • Assess its clinical significance
  • For transfusion
  • In pregnancy
38
Q

How do you identify an antibody?

A
  • Compare pattern of reactions with each reagent cell of ID panel with the pattern of antigens on the reagent cells
  • Matching pattern will identify the antibody
39
Q

What is zeta potential?

A

Positively charged ion cloud that surrounds RBC

40
Q

Why are RBCs unable to get close to one another?

A

Red cells cannot get close to each other due to the zeta potential

41
Q

What class of antibodies can span the gam between RBCs?

A

IgM antibodies can span the gap between RBCs

-Doesn’t need LISS

42
Q

What class can not span the gap between RBCs and so what do we use in order for this class of antibody to span the gap?

A

IgG cannot, because too small to overcome ZETA potential (+ve charge)

  • To overcome this LISS (Low Ionic Strength Saline) is used
  • LISS (low ionic strength saline) is negatively charged, so neutralises positive ZETA potential
  • Therefore IgG can now span the gap
43
Q

What does indirect anti-globulin test(IAT) detect?

A

Used to detect IgG antibodies

44
Q

Steps involved in IAT?

A
  1. LISS counteracts Zeta potential.

2. Results in agglutination

45
Q

What is IAT used for?

A
  1. Screening for antibodies
  2. Identifying antibodies
  3. Cross-matching donor blood with recipient plasma when there are known antibodies or a previous history of antibodies.
46
Q

Immediate spin cross-match

A
  • Antibody screen is negative
  • Checking donor red cells against patients plasma
    • ABO check
    • Incubate for 2 – 5 minutes (room temp), spin and read
47
Q

Full indirect antiglobulin test cross match

A
  • Antibody screen positive or patient has known antibody history
  • Select antigen negative donor red cells and incubate with patient serum for 15 minutes at 37oC
48
Q

ISX-basically checking the ABO group

A

Therefore IgM antibodies = no problem with ZETA potential = no need to IAT

49
Q

How many donations does the NHSBT collect?

A

NHSBT collects about 2 million donations per year

50
Q

What is the eligibility for blood donors?

A
  • 17 - 65 years old (first donation)

- Over 50kg

51
Q

What are concentrated RBCs packed in?

A

Concentrated red cells (packed cells) in a suspension of SAGM

52
Q

What do we activate if there’s significant bleeding?

A

If significant bleeding anticipated, activate the major haemorrhage protocol

53
Q

What does fresh frozen plasma contain?

A

FFP contains all clotting factors

54
Q

What is FFP given for?

A

Given for coagulopathy with associated bleeding

55
Q

What is FFP life after thawing?

A

Only has 24 hour life after thawing

56
Q

How many donors is an adult pool of platelets from?

A

Adult pool of platelets from 4 donors (suspended in plasma from 1 donor)

57
Q

What are platelets required to create?

A

Platelets required to create clots to reduce bleeding

58
Q

Why is patient history important in terms of platelets?

A

Some drugs given to reduce efficacy of platelets (anti-platelet agents) so patient history important

59
Q

What does cryoprecipitate contain?

A

Contains Factor VIII, VWF and fibrinogen

60
Q

How many units of cryoprecipitate is given at one time?

A

2 units usually given at one time

61
Q

What do we use to monitor fibrinogen levels?

A

Monitor fibrinogen levels by clotting screens

62
Q

Regulation of blood

A

EU Blood Safety Directive

Blood Safety Quality Regulations

Better Blood Transfusion 3

MHRA inspections

CPA inspections

63
Q

What is hemovigilance?

A

Surveillance procedures covering the entire blood transfusion chain

64
Q

Serious hazard of transfusion(SHOT)

A
  • Voluntary reporting

- Report all Serious adverse Events (SAE) and Serious adverse reactions (SAR)

65
Q

Serious adverse blood reactions and events(SABRE)

A
  • Mandatory reporting

- Report all SAR and SAE where the root cause error was the Quality system

Haematology (6 decks)

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