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Blood Bank: Spring 2024 > DAT > Flashcards

DAT Flashcards

1
Q

Distinguish between IAT and DAT

A

IAT: in vitro, test what has attached to cell in test system
DAT: in vivo, test what has attached to the cell in the body

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2
Q

When is DAT ordered?

A
  • Hemolysis present
  • Positive auto-control
  • Transfusion reaction workup
  • Cordblood eval
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3
Q

DAT is predictive of ____ by immune process in 83% of the population exhibiting symptoms

A

Hemolytic anemia

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4
Q

Interpretations of positive auto-control

A
  • DAT could be positive for IgG
  • Transfused cells are in pt sample
  • Autoimmune process
  • Contamination of AHG procedure
  • HDN/HTR
  • Drug-induced Ab
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5
Q

Interpretation of negative auto-control

A
  • DAT likely negative for IgG
  • Ab not reactive with pt’s own cells
  • Could be IgA or IgM or undetectable proteins
  • Weak reaction, Ab dissociated from cell
  • Complement could have destroyed cells before reaction
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6
Q

Principle of DAT

A
  • Uses anti-human globulin (against Fc portion of antibody) to detect presence of Ab on the RBCs themselves
  • No incubation step (no LISS inc)
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7
Q

Implications if check cells don’t work

A

Not enough washes

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8
Q

Inert control

A

Pt RBCs that you didn’t add AHG reagent to -> expect no agglutination bc cells shouldn’t be spontaneously clumping

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9
Q

AHG reagent

A
  • polyspecific anti-human-globulin
  • human/rabbit IgG + murine monoclonal anti-C3b, C3d (anti-complement)
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10
Q

Check cells in DAT

A
  • Coomb’s control cells with anti-IgG
  • Complement control with C3 attached
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11
Q

Why can failure to add AHG reagent quickly cause false negative?

A

Because complement/IgG can start to fall off the cell and dissolve in the plasma

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12
Q

In order to be a DAT, it must detect what?

A

Both complement and IgG on cell

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13
Q

Possible reasons for positive anti-C3b, C3d reaction

A
  • HTR
  • Drug-induced Ab
  • Cold autoimmune anemia
  • Complement activation due to bacterial infection or auto-Ab
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14
Q

Possible reasons for positive anti-IgG reaction

A
  • HTR from allo-Ab
  • HDN
  • Drug-induced Ab
  • Warm autoimmune anemia
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15
Q

PCH

A

Donath-Landsteiner IgG auto-Ab reacts with RBCs in the coldest parts of the body, which causes irreversible complement binding

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16
Q

Cold Agglutinin Syndrome (CAS)

A

Cold-reactive IgM auto-Ab binds complement as RBCs return to warmer part of the body, when IgM dissociates and leaves RBCs coated with complement

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17
Q

Warm Autoimmune Hemolytic Anemia (WAIH)

A

Auto-Ab reacts with patient’s RBCs in vivo, may or may not activate complement

18
Q

Biggest reason to perform elution?

A

ONLY when positive DAT with anti-IgG!
Not positive DAT and anti-C3d! Need the anti-IgG!

19
Q

Reasons to do elution

A
  • Positive DAT and anti-IgG
  • HTR workup
  • HDN
  • Confirm presence of specific Ag on RBCS, use in conj. with adsorption
  • Confirm Ab specficity by showing it can be adsorbed onto RBC of only a particular blood group phenotype
20
Q

Elution principle

A

Remove and ID Ab coating red cells

21
Q

Elution steps

A
  1. Wash 20 drops of whole blood cells 4x
  2. Remove IgG from cell
  3. Make solution containing antibody testable for cells
  4. Perform Ab ID
22
Q

In elution, what do you destroy and preserve?

A

Destroy cells, preserve Ab

23
Q

Why do you save the supernatant from the last elution wash?

A
  • To test it against screen or panel cells in the same method as eluate -> expect negative result
  • Positive result = invalid
24
Q

Interpretation of negative elution results

A
  • Non-RBC Ab
  • Low incidence IgG
  • Weak IgG
25
Q

Interpretation of “some positive” elution results

A
  • Delayed HTR
  • HDN
  • New Ab formation
26
Q

Interpretation of positive elution results

A
  • Warm auto-Ab (most likely)
  • HTR due to high incident Ab
  • HDN due to high incident Ab
  • Drug-induced Ab
27
Q

Interpretation of mixed-field elution results

A

INVALID
You didn’t bring eluate to serological conditions or there’s interfering substances present

28
Q

Interpretation of last wash positive in elution protocol

A

Inadequate washing, remake eluate

29
Q

List elution methods

A
  • Acidic
  • Heat or freeze-thaw
  • Organic solvents to reduce surface tension
30
Q

T/F
Treatment of sensitized RBCS causes the dissociation of AB into the eluate

A

True

31
Q

Which is done first?
elution or adsorption?

A

Adsorption

32
Q

Who orders adsorption?

A

Blood banker only
Not clinician

33
Q

Adsorption main purpose

A

Remove auto-Ab in order to ID underlying allo-Ab

34
Q

Several purposes for adsorption

A
  • Separate multiple Ab in plasma
  • Confirm presence of specific Ag on RBCs (conj with elution)
  • Confirm specificity of Ab by showing it can be adsorbed onto RBCs of only a particular blood group phenotype
35
Q

Adsorption principle

A

Purposely coat red cells with Ab

36
Q

Difference between elution and adsorption

A

Elution = take Ab off red cells
Adsorption = put Ab onto red cells

37
Q

2 types of adsorption used to remove warm Ab and when you use them

A
  • Autoadsorption: when patient has NOT been transfused
  • Differential adsorption: when patient has been transfused
38
Q

Differential adsorption

A

Adsorb patient plasma to 3 different known cell types

39
Q

Adsorption controls

A

Test adsorbed plasma against patient cell (auto) or screen cells (differential) to make sure all Ab have been removed from plasma

40
Q

T/F
Auto-control always indicates presence of auto-Ab

A

False

41
Q

T/F
DAT may be positive with transfused cells only

A

True

42
Q

Elution of transfused cells will indicate what?

A

Delayed HTR

Blood Bank: Spring 2024 (10 decks)

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