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Immunohematology > AHG/Coombs (Lab) > Flashcards

AHG/Coombs (Lab) Flashcards

1
Q

AHG is obtained from ___________

A

immunized non human species (rabbits/guinea pigs) that binds to IgG or complement from Px serum or RBC

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2
Q

The type of Ab generated and used nowadays for AHG is ___________

A

monospecific AHG/monoclonal Abs

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3
Q

A monospecific AHG contains ________________

A

a single component AHG (either Anti-IgG, Anti-C3). Only one reagent per vial = cannot be both IgG and complement

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4
Q

Monospecific Ab is produced through _____________

A

hybridoma technology (spleen and cancer cells)

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5
Q

A polyspecific AHG contains __________________

A

multiple components (Anti-IgG + Anti-C3)

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6
Q

In AHG testing, this is employed to aid visualization of Ag-Ab reaction

A

AHG sera

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7
Q

What are the two methods of AHG test?

A

Direct and Indirect AHG test

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8
Q

This method of AHG test combines known Ag/Ab with either plasma/cells w/ known component

A

Indirect method

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9
Q

In indirect method, it detects _____________

A

either Ag or Ab depending what is needed and detects in-vitro sensitization

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10
Q

What is the specimen for indirect AHG test?

A

Donor Red cell and Patient’s Serum

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11
Q

What is the enhancement medium used for indirect AHG test?

A

22% bovine albumin

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12
Q

TRUE OR FALSE:

POSITIVE reaction indicates the absence of Abs in Px serum

A

FALSE

POSITIVE reaction indicates presence of circulating Abs causing sensitization to red cell

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13
Q

TRUE OR FALSE:

NEGATIVE results require addition of check cells/coomb’s cells

A

TRUE

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14
Q

What are the uses of indirect AHG test?

A 
employed during crossmatching
detection/odentification of unexpected Abs
red cell phenotyping
investigation of transfusion reaction
detecting weak D (Du)
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15
Q

What is the difference between direct and indirect AHG test?

A

Direct AHG test only has a single step procedure (no incubation)
detects Abs coating red cells in vivo (in vivo sensitization)
test for certain clinical conditions

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16
Q

The specimen used for direct AHG test is _________________

A

RBC

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17
Q

What are the uses of direct AHG test?

A

diagnosis of HDN
diagnosis of AIHA, CAIHA, WAIHA
investigation of transfusion reaction
detection of red ell sensitization reactions caused by drugs

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18
Q

What are the examples of drugs that can cause red cell sensitization?

A

Penicillin
Methyldopa
Cephalothin

19
Q

In detecting Weak D, ______ portion of Ab attach to ______ portion of IgG or complement

A

Fab, and Fc

20
Q

What are the factors in the sensitization phase (in vitro) affecting AHG test?

A

temperature - must be 37 deg C

incubation time - 30-120mins (saline/NSS) or 10-15 (LISS)

ratio of serum to cells - 40:1 or 133:1

reaction medium - (Albumin/LISS/PEG)

21
Q

TRUE OR FALSE:

In the sensitization phase, INC ratio leads to DEC sensitivity

A

FALSE

INC ratio = INC sensitivity

22
Q

This reaction medium affects the 2nd step of reaction and allows Ab-coated cells to come closer w/ each other

A

Albumin

23
Q

This reaction medium affects the sensitization stage that enhances Ab uptake and removed negativity

A

LISS

24
Q

This reaction medium is a water soluble linear polymer and is also used for increase Ab uptake

A

PEG

25
Q

In the washing phase, what is the ideal solution for washing?

A

Fresh/buffered saline

DEC pH during storage = acidic = affect

26
Q

What is the relative centrifugal force and time when observing hemagglutination reaction?

A

1000 rcf for 20secs

500 RCF for 15 to 20 secs.
3400 RPM for 15-20 secs.

27
Q

If the tapping of the tube is vigorously the result may be interpreted as ______________

A

FALSE +

28
Q

Over centrifugation is cause false ____________

A

positive

29
Q

Use of dirty glassware causes false ____________

A

positive

30
Q

If the red cells agglutinated before washing step and addition of AHG, it causes false ___________

A

positive

31
Q

AHG reagent not immediately added causes false ____________

A

negative

32
Q

Loss of reagent activity causes false ____________

A

negative

33
Q

Inappropriate red cell concentrations causes false ___________

A

negative

34
Q

Bacterial contamination causes false ___________

A

negative

35
Q

In DAT/IAT, how long will the tube be centrifuged?

A

15 secs at 3400rpm

36
Q

In IAT, the unknown test tube contains _________

A

2 drops of unknown serum and 2 drops 3% RCS

37
Q

In IAT, the negative control test tube contains _________

A

2 drops of 22% BSA and 2 drops 3% RCS

38
Q

What is the anticoagulant used for DAT?

A

EDTA to prevent complement activation

39
Q

At what time and temperature will the tubes be incubated in IAT?

A

37 deg C water bath for 15mins

40
Q

Which AHG test method is used to detect Du?

A

IAT

41
Q

The presence of weak D can be demonstrated by ____________________

A

incubating red cell suspension with Anti-D followed by antiglobulin testing

42
Q

In detecting Du, it must be incubated at 37 deg C for 15mins to _____________

A

facilitate sensitization

43
Q

In detecting weak D, the agglutination must be a grade of _____________

A

2+ to be considered as true negative

if 1+/mf = invalidate result

Immunohematology (7 decks)

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