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Y2 Immunological Disorders > TRANSFUSION Week 8 !!! > Flashcards

TRANSFUSION Week 8 !!! Flashcards

1
Q

What does AIHA stand for?

A

Autoimmune Haemolytic Anaemia

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2
Q

What are the clinical symptoms of AIHA?

A

Very low Hb levels

Positive DAT and other indications of haemolysis

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3
Q

Outline what happens in an indirect Coombs or anti globulin test.

A

Donors blood sample is added to a recipients serum containing antibodies of known phenotype.

Recipient antibodies that target the donor red blood cells form antibody-antigen complexes.

Anti-human globulin is added to the solution.

Agglutination of red blood cells occurs because human antibodies are attached to red blood cells.

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4
Q

What is the purpose of the direct Coombs test?

A

To see if a patient has any autoantibodies.

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5
Q

Outline what happens in a direct Coombs or anti globulin test.

A

Blood sample from a patient with haemolytic anaemia is taken.

The patients washed red blood cells are then incubated with antihuman antibodies.

RBCs agglutinate and form links between the red blood cells by binding to the human antibodies on red blood cells.

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6
Q

What is the main purpose of a DAT test?

A

To look for the type of antibody attached to the human red cells.

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7
Q

What does DAT stand for?

A

Direct antiglobulin test

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8
Q

What is the role of complement in AIHA?

A

IgG antibodies can attach to antigens on red cells and trigger the complement cascade.

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9
Q

At what stages can the complement cascade stop when causing AIHA?

A

At the C3 stage.

But may often go to completion where a channel is formed in the red cel membrane and there is lysis.

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10
Q

What happens if the classical pathway of complement stops at the C3 stage during AIHA?

A

Macrophages in the liver will cause destruction of autoantibodies.

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11
Q

What happens if the complement cascade continues past the C3 stage during AIHA?

A

Intravascular haemolysis occurs and free Hb is released. This causes a positive feedback system and may cause severe reactions.

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12
Q

What activates the classical pathway of complement in terms of AIHA?

A

Antigen-antibody immune complexes

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13
Q

What activates the alternative pathway of complement in terms of AIHA?

A

Spontaneous activation

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14
Q

How is extravascular haemolysis encouraged as part of complement in terms of AIHA?

A

C3b coats RBCs and facilitates their destruction in the liver.

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15
Q

How is intravascular haemolysis encourages as part of complement in terms of AIHA?

A

A pore called MAC forms into the RBC membrane which causes their destruction by lysis in the blood. Release of here from RBCs can activate the alternative complement pathway as a second hit.

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16
Q

What is the most common classification of AIHA?

A

Warm AIHA

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17
Q

What antibodies cause warm AIHA?

A

IgG

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18
Q

What is the optimal reaction temperature for warm AIHA?

A

37 degrees celsius.

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19
Q

Does warm AIHA use complement?

A

It can

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20
Q

Is warm AIHA DAT positive or negative?

A

+

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21
Q

What are the results of a DAT test for warm AIHA?

A

IgG+

C3b -

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22
Q

In terms of warm AIHA, where are red cells coated with IgG destroyed?

A

The spleen

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23
Q

What additional antibodies may warm AIHA cause?

A

IgM and IgA

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24
Q

In warm AIHA, if complement is added, what happens?

A

More rapid cell destruction occurs in the liver.

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25
Q

Do IgG antibodies have placental transfer?

A

Yes

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26
Q

Do IgG antibodies cause primary immune responses? If yes, what strength?

A

Yes - weak

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27
Q

Do IgG antibodies cause secondary immune responses? If yes, what strength?

A

Yes - ver strong

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28
Q

What are the common causes of IgG mediated warm AIHA?

A

Idiopathic
Autoimmune disorders
Lymphoproliferate disorders

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29
Q

Name some of the treatments for warm AIHA

A

Corticosteroids

Splenectomy

Treatment of any present underlying disorders

Immunosupressive agents

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30
Q

Is cold AIHA common or rare?

A

Rare

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31
Q

What is the antibody cause of cold AIHA?

A

Cold-reacting IgM autoantibodies

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32
Q

What other possible antibodies can be the causes of cold AIHA?

A

Anti-i or Anti-I

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33
Q

What happens with Anti-I or anti-i autoantibodies in a blood sample and how does this affect testing? (In terms of cold AIHA)

A

As someone has a blood sample taken, it begins to cool down and is room temperature by the time it reaches the lab. This means autoantibodies can give a positive agglutination reaction which is not true positive in the body. This creates false positives.

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34
Q

What is used to prevent false positives in terms of testing for cold-AIHA?

A

Control wells

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35
Q

Do IgM antibodies have placental transfer?

A

No

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36
Q

Do IgM antibodies cause complement activation?

A

Yes

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37
Q

What is the optimal reaction temperature for cold AIHA?

A

4-20 degrees celcius.

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38
Q

What is the strength of the primary immune response to IgM antibodies?

A

+++

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39
Q

What is the strength of the secondary immune response to IgM antibodies?

A

+

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40
Q

What are the clinical manifestations of cold AIHA?

A

Triggered by cold exposure

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41
Q

What are the common causes of cold AIHA?

A

Idiopathic

Infection

Lymphoproliferate disorders

42
Q

What are the possible treatment options for cold AIHA?

A

Avoidance of cold exposure

Treatment of underlying disorder if present

Plasma exchange at temporising measure

43
Q

What causes haemoglobinuria in cold AIHA?

A

As blood returns from warmer parts of the body from the peripheral capillaries, the antibody elutes from the cells. The complement cascade has already been started, and in some cases, goes to completion resulting in intravascular lysis or rapid lysis of the C3b-coated cells in the liver.

44
Q

What does PCH stand for?

A

Paroxysmal Cold Haemogloburia

45
Q

How is PCH different to cold AIHA?

A

It is not caused by IgM antibodies

46
Q

Describe the causative antibody in PCH.

A

Bi-phasic IgG antibody with anti-P specificity.

(Donath Lansteiner antibody).

47
Q

Describe how the Donath-Lansteiner antibody works in different temperatures.

A

The antibody reacts in the cold but activates complement in the warm leading to haemolysis and haemoglobinuria.

48
Q

What test is used to detect antibodies in terms of PCH?

A

Donath-Landsteiner test

49
Q

Outline how the Donath-Landsteiner test works.

A

Group O cells are incubated with the patient serum at 0 degrees ceclius and then at 37 degrees celsius with a control.

Haemolysis indicates a positive test result.

50
Q

What indicates a positive test result in the Donath - Landsteiner test?

A

Haemolysis

51
Q

When is PCH most common in children?

A

Post virally

52
Q

What is haemoglobinuria?

A

The presence of excess Hb in urine.

53
Q

What is Passenger lymphocyte syndrome in terms of AIHA?

A

AIHA following non-ABO identical bone marrow or solid transplant.

54
Q

What is the onset time of passenger lymphocyte syndrome?

A

5-15 days post transplant.

55
Q

What are the clinical identifiers of passenger lymphocyte syndrome?

A

Rapidly falling Hb

Renal failure

Negative antibody screen

DAT positive

Anti-A or Anti-B detected in the back group.

56
Q

Describe the possible mechanisms of Drug or associated AIHA.

A

Drug adsorption: antibodies react to drug coating the red cell.

Immune Complex: Formation of drug-antibody immune complexes attached to the cell surface

Drug independent autoantibodies: Drug stimulates the production of the autoantibody.

57
Q

What type of drug associated AIHA mechanism can appear as warm AIHA?

A

Drug independent autoantibodies.

58
Q

Outline what occurs briefly to cause passenger lymphocyte syndrome.

A

Transfer of donor lymphocytes.

Donor B cells recognise recipients red blood cells.

Primary or secondary immune response with IgG production.

DAT + Haemolysis.

59
Q

In terms of drug associated AIHA, what type of haemolysis occurs when the hapten model occurs?

A

Haemolysis by complement or phagocytosis.

60
Q

What is the hapten model of drug associated AIHA?

A

Drug + Red blood cell = Hamolysis of RBC by complement or phagocytosis

61
Q

In terms of drug associated AIHA, what type of haemolysis occurs when an immune complex is formed?

A

Haemolysis by complement.

62
Q

What is the immune complex model of drug associated AIHA?

A

Immune complex (Drug, carrier protein, C3b and antibody against drug).

This binds to C3b receptors on red blood cells and causes haemolysis by complement.

63
Q

What is the autoimmune model of drug associated AIHA?

A

Antibodies against a drug bind with normal RBC antigens and cause haemolysis by phagocytosis.

64
Q

In terms of drug associated AIHA, what type of haemolysis occurs when an autoimmune complex is formed?

A

Haemolysis by phagocytosis

65
Q

What is the elution method for diagnosing AIHA?

A

A method to remove bound antibody from red cell membranes for identification.

66
Q

Outline the process of elution to diagnose AIHA.

A

Labs use strong acid.

Antibodys are removed from the acid and quickly buffered to prevent denaturation.
Resulting equate is incubated with panel cells fro identification.

67
Q

What is a pan-agglutinin ?

A

An agglutinin that reacts with all human red cells.

68
Q

What is the adsorption method for diagnosing AIHA?

A

Removing autoantibodies and allowing detecting and identification of any alloantibodies present.

69
Q

How is all adsorption carried out in terms of diagnosing AIHA?

A

Incubate patient’s plasma with donor reagents of known phenotype. Autoantibodies are removed as they stick to red cells.

70
Q

How is auto adsorption carried out in terms of diagnosing AIHA?

A

Incubate patient’s plans with their own red cells. Alloantibodies will stick to red cells and can then be removed.

71
Q

In adsorption methods to find AIHA, describe the plasma used for cross matching.

A

It will be ‘suitable for’ rather than compatible because we will be unsure if any alloantibodies have been removed.

72
Q

In terms of adsorption to find AIHA diagnosis, why do we often not know if alloantibodies have been removed?

A

Autoantibodies can mask alloantibodies.

73
Q

In a blood film or haematology sample to AIHA, what do polychromatophillic red cells indicate?

A

Immature red cells and therefore an increase in red cell production.

74
Q

In a blood film or haematology sample to AIHA, what do spherocytes indicate?

A

Red cell membrane abnormalities due to splenic macrophages removing attached antibodies.

75
Q

In a blood film or haematology sample to AIHA, what do schistocytes indicate?

A

Red cell lysis is occurring.

76
Q

What are schistocytes?

A

Red cell fragments due to lysis.

77
Q

In a blood film or haematology sample to AIHA, what do nucleated red blood cells indicated?

A

An increase in red cell production, so rapid that maturation is taking place in the peripheral circulation rather than the bone marrow.

78
Q

What does the lab term “cold aggs” ?

A

A blood film where red cells are bound together with IgM autoantibodies. This appears to look like an agglutination reaction.

79
Q

In what ways may AIHA change the full blood count of a patient?

A

Hb decreased

Mean cell volume decreased

Increased cold aggs

80
Q

What happens to the mean cell Hb concentration in cold aggs?

A

Increases.

81
Q

How does AIHA change the haptoglobin found in a patient sample and why?

A

Decreases - because it binds to free Hb which is found due to haemolysis.

82
Q

How does AIHA change the lactate dehydrogenase found in a patient sample?

A

Increases - released from lysis of RBCs.

83
Q

How does AIHA change the peripheral blood smear of a pateient and why?

A

Abnormal RBCs based on cause of anaemia.

84
Q

How does AIHA change the reticulocyte count of a patient and why?

A

Increased by the marrows response to anaemia.

85
Q

How does AIHA change the uncojugated bilirubin of a patient and why?

A

Increased due to increased haemoglobin breakdown.

86
Q

How does AIHA change the urinalysis of a patient and why?

A

Urobilinogen positive for blood due to free Hb and its metabolites.

87
Q

In what type of patients in hyperhaemolysis most common?

A

Those with sickle cell disease.

88
Q

Describe what characterises hyperhaemolysis

A

Destruction of transfused and compatible red cells and those of the recipient.

89
Q

In hyperhaemolysis patients, will post-transfusional or pre-transfusion Hb be lower?

A

Post

90
Q

What would be the effect of further transfusion on hyperhaemolysis?

A

Exacerbation of the haemolysis possibly leading to fatality.

91
Q

What is the treatment of hyperhaemolysis?

A

Steroids and/or an Iv of Ig

92
Q

What type of feedback system is hyperhaemolysis?

A

+ve

93
Q

Why do we transfused RhD and Kell matched blood to patients with AIHA?

A

This is to try to prevent the formation of allobodies if autoantibodies are present.
This will also lessen any reaction to any masked, undetected alloantibodys.

94
Q

The direct anti globulin test is used to detect red cell autoantibodies. True or false?

A

True

95
Q

Warm AIHA is usually associated with IgG. True or false?

A

True

96
Q

Cold AIHA is usually associated with IgG antibodies. True or False?

A

False

97
Q

What’s unusual about the antibody involved in PCH?

A

It is bi-phasic and has anti-P specificity

98
Q

what group of blood should be transfused to a patient suffering with passenger lymphocyte syndrome?

A

O

99
Q

PCH is associated with post viral infections in children. True or false?

A

True

100
Q

AIHa is more common in men than women. True or false?

A

False

101
Q

If you have drug independent AIHA but this appears as warm AIHA, what would a clinician do to identify the difference?

A

Medics would look at patients medical history to see what drugs they have previously taken that would cause a drug and therefore not warm AIHA.

102
Q

Why do we transfuse the same Rh and Kell groups even though the patient may have Rh or Kell auto-antibody?

A

To prevent someone with autoantibodies forming alloantibodies as well. Rh and Kell antibodies are most likely to cause serious transfusion reactions so giving these prevents reactions.

Y2 Immunological Disorders (9 decks)

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