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Transfusion Science > Lecture 8 - AIHA > Flashcards

Lecture 8 - AIHA Flashcards

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1
Q

what is the first clinical sign of AIHA?

A

very low Hb level

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2
Q

what test will be positive when a patient has AIHA?

A

direct antiglobulin test

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3
Q

what is the indirect anti globulin test?

A

patients serum is obtained and incubated with donors blood sample, antihuman Its added to test for agglutination

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4
Q

what is direct antiglobulin test?

A

blood taken directly from the patient and added with antihuman Ig, when antibodies or complement still on blood cells

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5
Q

how is classical complement activated?

A

by autoantibodies that bind to red cell antigens and form complex

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6
Q

what occurs when complement cascade ends at C3?

A

macrophages in the liver recognise this as being abnormal and the cells are destroyed, which is extravascular haemolysis

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7
Q

what is intravascular haemolysis and how is it caused?

A

destroyed in the blood vessel when goes past C3

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8
Q

how is warm AIHA characterised?

A

most common, IgG antibody at 37 degrees, DAT is positive with IgG +/- C3b

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9
Q

how are cells destroyed in warm AIHA?

A

red cells coated with IgG are destroyed in the spleen, if complement activated then more rapid destruction in the liver

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10
Q

what antibodies can sometimes be related to warm AIHA?

A

IgM or IgA

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11
Q

are the autoantibodies in warm AIHA specific?

A

usually react with all red cells yet sometimes can have Rh related specificity

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12
Q

how is cold AIHA characterised?

A

rarer, caused by a cold reacting IgM autoantibody

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13
Q

what specificity are cold AIHA usually?

A

often anit-I or anti-i

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14
Q

how can the thermal aptitude of cold AIHA increase?

A

following an infection such as glandular fever

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15
Q

where do cold AIHA antibodies usually react?

A

in capillaries where the blood is cooler

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16
Q

how can cold AIHA antibodies affect blood grouping?

A

gives false positives as when blood grouping occurs, the autoantibodies react with everything

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17
Q

how can a partial complement cascade occur in cold AIHA?

A

when the blood returns to warmed parts of the body, the antibody elutes from the red cell

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18
Q

how does IV lysis occur in cold AIHA?

A

the C3b coated cells are removed in the liver

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19
Q

what does IV lysis in cold AIHA lead to?

A

haemoglobinuria after exposure to the cold

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20
Q

how is paroxysmal cold haemoglobinuria characterised?

A

usually as cold AIHA but not caused by IgM antibodies

21
Q

what is the causative antibody in paroxysmal cold haemoglobinuria?

A

bi-phasic IgG antibody with anti-P specificity

22
Q

how can paroxysmal cold haemoglobinuria be tested for?

A

group O cells are incubated with patient serum at 0 degrees then at 37 with a control, haemolysis shows a positive result

23
Q

what is passenger lymphocyte syndrome?

A

donor B lymphocyte production of antibodies causing an immune reaction

24
Q

how is passenger lymphocyte syndrome caused?

A

following non-ABO identical bone marrow or solid organ transplant

25
Q

how long is the onset for passenger lymphocyte syndrome? what does onset look like?

A

5-15 days, rapidly falling Hb and possible renal failure

26
Q

what will the test results be for passenger lymphocyte syndrome?

A

antibody screen will be negative, yet direct antibody test positive, anti-A or anti-B detected in back grouping

27
Q

how can detection of passenger lymphocyte syndrome be monitored?

A

serologically cross match for anti-A/B for life with bone marrow and for 3 months with transplant

28
Q

what blood should be given to those with passenger lymphocyte syndrome?

A

O

29
Q

what are the mechanisms of drug induced AIHA?

A

drug adsorption, immune complex or drug independent antibodies

30
Q

how does drug adsorption cause drug associated AIHA?

A

antibodies in the body react with the drug coating red cells

31
Q

how do immune complexes cause drug associated AIHA?

A

formation of drug-antibody complexes attached to the cell surface causing severe haemolytic episodes due to complement activation

32
Q

how do drug independent antibodies cause drug associated AIHA?

A

drug stimulated the production of autoantibodies, appears as warm AIHA

33
Q

how can you use elution to identify antibody specificity?

A

remove antibodies using strong acid, buffer them and test against panel cells for agglutination

34
Q

how can adsorption be used tonidentity antibodies?

A

remove autoantibodies to check for alloantibodies

35
Q

what is allo-adsorption?

A

incubate patients plasma with known donor cells so autoantibodies are adsorbed onto the red cells

36
Q

what is auto-adsorption?

A

incubate patients plasma with own cells which removes any autoantibodies when the red cell is removed, so only alloantibodies are left behind

37
Q

what do polychromatophillic red cells indicate on the blood film?

A

indicate immature red cells and increase red cell production

38
Q

what do spherocytes indicate on a blood film?

A

indicate red cell membrane abnormalities due to splenic macrophages removing attached antibodies

39
Q

what do schistocytes indicate on a blood film?

A

red cell lysis due to being red cell fragments

40
Q

what do nucleated red blood cells indicate on a blood film?

A

indicate increased red cell production that is so rapid that the maturation is occurring peripherally rather than in bone marrow

41
Q

what happens to haptoglobin in haemolysis?

A

decreased as binds to free haemoglobin

42
Q

what happens to lactate dehydrogenase in heamolysis?

A

elevated due to being released during red cell lysis

43
Q

what happens to reticulocyte count during haemolysis?

A

increased due to marrow responding to anaemia

44
Q

what blood should be transfused if patients with AIHA have an underlying antibody?

A

Rh or K matched to prevent formation of alloantibodies

45
Q

what is hyperhaemolysis?

A

destruction of transfused and own cells

46
Q

what is the treatment of hyperhaemolysis?

A

steroids or IV Ig

47
Q

what are the possible mechanisms of hyperhaemolysis?

A

bystander lysis or hyperactive macrophages?

48
Q

what is bystander lysis?

A

possibly a HLA antibody that activates complement which attached to own and donor cells

49
Q

what are hyperactive macrophages?

A

they destroy own and donor red blood cells

Transfusion Science (8 decks)

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