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Immunohematology > Immune Hemolytic Anemias > Flashcards

Immune Hemolytic Anemias Flashcards

1
Q

immune hemolytic anemia

A

shortening of RBC survival due to antibodies coating the red cells
anemia of increased destruction

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2
Q

Immune Hemolytic Anemias requiring transfusion support (3 categories)

A
  1. Alloimmune hemolytic anemia
  2. Autoimmune hemolytic anemia
  3. Drug-induced hemolytic anemia
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3
Q

Lab indicators of immune hemolysis

A 
positive DAT
increased retics
increased LDH-intravascular hemolysis
increased indirect bilirubin
decreased hemoglobin & hematocrit
decreased haptoglobin
spherocytes -extravascular
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4
Q

Intravascular hemolysis

A

increased bilirubin
hemoglobinuria, hemoglobinemia
positive DAT
schistocytes

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5
Q

Extravascular hemolysis

A

increased bilirubin
no hemoglobinuria, no hemoglobinemia
positive DAT
spherocytes

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6
Q

Extravascular targeting of Coated RBCs

A

A. reticular endothelial system (RES) can ‘pluck’ IgG-coated RBCs & create spherocytes
B. RES can engulf & phagocytize RBCs IgG-coated RBCs in the spleen
C. RES can remove IgG & Complement coated RBCs in the liver

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7
Q

Direct Antiglobulin Test

A

detect IgG &/or complement attached to the red cell surface
up to 90 molecules of IgG may be present normally

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8
Q

threshold for positive DAT

A

100-500 molecules of IgG

400-1100 molecules of C3d

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9
Q

reasons for positive DAT besides the obvious

A

0.3-1.0% of hospitalized pts will have a positive DAT w/o clinical hemolysis
IVIG!!!
recent transfusion
drug associated w/ immune hemolytic anemias
organ transplant
septicemia-bc of constant complement activation

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10
Q

DAT tips for accuracy

A

RBCs must be washed thoroughly = false negative
RBCs must be tested immediately after washing to avoid false negatives
used EDTA sample to avoid false positive

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11
Q

Additional testing when autoantibodies are present

A
  1. elution when DAT IgG is positive

2. absorption: remove warm/cold autoantibody

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12
Q

Autoantibodies general

A

must resolve cold autos in order to ABO type
must resolve warm autos in order to screen for alloantibodies
serologic findings DO NOT always imply hemolytic anemias
clinical significance varies

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13
Q

how to predict if autoantibodies are clinically significant

A

thermal range - high range cold autos & warm autos
ability of antibody to fix complement
titer of antibody bound to RBCs
underlying disease

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14
Q

Cold Autoagglutinin Disease

A

hemolytic anemia associated w/ autoantibodies reacting in the cold
18% of all AIHAs
acute & chronic

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15
Q

Acute CAD

A

usually fairly mild anemia
anti-I: can happen in mycoplasma pneumonia & other bacterial infections
anti-i: CMV, infectious mononucleosis etc

usually do not require any transfusion support

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16
Q

chronic CAD

A

most serious clinically
more common in the elderly, lymphoma, chronoic lymphocytic leukemia
most severe cases in younger individuals w/ no known underlying cause

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17
Q

CAD clinical features

A 
anemia 
jaundice
acrocyanosis
Raynaud's phenomenon
therapy: avoid cold
18
Q

CAD manifestation/mechanism

A
  1. IgM antibody binds to RBC in lower temps of peripheral circulation causing complement to attach to RBCs
  2. as RBCs move to warmer areas, IgM dissociates but complement remains
  3. intravascular hemolysis
19
Q

CAD serologic testing

A

can interfere with serologic testing- wash cells
usually can skip this step for antibody screen/panel/crossmatch
prewarming techniques

20
Q

typical reactivity seen with CAD

A 
4C= 3-4+
15-18C= 1-2+
20-24C = 0-1+
37C = 0
IgG = 0
21
Q

CAD lab results

A

positive DAT - anti-C3d
reticulocytosis
agglutination in peripheral smear- have to warm up sample before testing

22
Q

Anti-I: pathologic

A

greater thermal amplitude >30C

titer >1000 @ 4C (always titer at 4C)

23
Q

other cold autoantibodies

A

anti-H & anti-IH: present in only A1 & A1B individuals at low levels
clinically insignificant unless in a BOMBAY phenotype
anti-M

24
Q

anti-M cold autoantibody

A

not uncommon in children less than 1 year old

25
Q

Paroxysmal Cold Hemoglobinuria (PCH)

A

uncommon; occurs in children after viral illnesses
biphasic hemolysin (anti-P): binds at low temps & causes hemolysis @ 37C
DONATH-LANDSTEINER TEST

26
Q

PCH treatment

A

normally self-limiting after virus passes
anti-P negative blood is rare-> transfuse w/ ABO compatible blood w/ blood warmer
treat w/ steroids

27
Q

Warm autoimmune hemolytic anemia

A

majority of AIHA
most detected are not clinically significant (no hemolysis)
important because they can mask an underlying alloantibody & will make crossmatches incompatible

28
Q

WAIHA serologic reactions

A 
IS - 0 
37C - 0
AHG - 2-4+
polyspecific DAT - 2-4+
IgG DAT - 2-4+
C3b/d DAT- 0-2+
29
Q

most common warm autoantibody

A

anti-e

30
Q

work around warm autoantibodies

A

perform an autoadsorption- cannot have had a transfusion recently

31
Q

mixed-type autoimmune hemolytic anemia

A

features similar to both warm & cold

DAT - both IgG & C3d/b

32
Q

Drug Induced Immune Hemolytic anemia

A

rare; first seen in penicillin & methyldopa

>100 drugs could cause IHA &/or positive DAT

33
Q

DIIHA mechanisms (4)

A
  1. penicillin-type (drug adsorption)
  2. immune complex
  3. membrane modification
  4. drug-independent
34
Q

Penicillin type DIIHA

A

penicillin or its metabolites are adsorbed onto the RBCs
antibodies attach to the drug causing a positive DAT (IgG) & may increase RBC destruction
hemolysis is extravascular
elute should be tested w/ RBCs sensitized w/ penicillin

35
Q

immune complex DIIHA

A

after patient receives a drug, an antibody to the drug forms
drug-antibody complex absorbs to the RBCs
complement is activated
intravascular hemolysis w/ hemoglobinemia & hemoglobinuria

36
Q

classic drugs that cause immune complex DIIHA

A

quinine

quinidine

37
Q

non-immunologic protein adsorption (Membrane modification)

A

drugs that MODIFY THE CELL MEMBRANE of RBCs by making the membrane ‘sticky’
positive DAT may demonstrate IgG, IgM, IgA, C3
rarely associated with RBC destruction
eluates are non-reactive bc there is no drug antibody present

38
Q

unique feature of drug-independent DIIHA

A

the drug does NOT have to be present to have a positive DAT

39
Q

methyldopa

A

anti-hypertensive drug; interferes with suppressor T cell function, leading to the production of autoantibodies

40
Q

Drug Independent features DIIHA

A

positive DAT - IgG; after 3-6 months of discontinuing the drug
eluate is reactive against all panel cells!
looks exactly like a warm autoantibody
hemolysis RARELY occurs

Immunohematology (16 decks)

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