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BB Lab (SF) > Anti-Human Globulin Testing > Flashcards

Anti-Human Globulin Testing Flashcards

1
Q

Antihuman Globulin test is also referred as ___

A

Coombs’ Test

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2
Q

The principle of AHG is that antihuman globulins obtained from immunized nonhuman species bind to human globulins such as ___ or ___ , either free in serum or attached to antigens on red blood cells (RBCs).

A

IgG or Complement

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3
Q

The AHG test is an essential testing methodology for __ medicine.

A

transfusion medicine

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4
Q

2 major types of blood group antibodies

A

IgM and IgG

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5
Q

Because of their large pentameric structure, _ antibodies bind to corresponding antigen and directly agglu- tinate RBCs suspended in saline

A

IgM

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6
Q

Some _ antibodies are termed nonagglutinating, or incomplete antibodies, because their single monomer structure is too small to directly agglutinate sensitized RBCs

A

IgG

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7
Q

Adding AHG reagent containing anti-IgG to RBCs sensitized with IgG antibodies allows for _ of these sensitized cells

A

hemagglutination

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8
Q

Antiglobulin tests detect _ or complement-sensitized RBCs.

A

IgG

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9
Q

2 types of AHG test

A

Direct Antiglobulin test – in vivo
Indirect Antiglobulin test – in vitro

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10
Q

In 1946, Coombs and coworkers2 described the use of AHG to detect __ __ sensitization of the RBCs of neonates suffering from hemolytic disease of the fetus and newborn (HDFN)

A

in vivo

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11
Q

The Coombs’ test involved the injection of human serum into rabbits to produce __ serum.

A

antihuman serum

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12
Q

The antiglobulin test can be used to detect RBCs sensitized with IgG __ , IgG __, and complement components.

A

IgG alloantibodies, IgG autoantibodies

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13
Q

The use of AHG to detect in vitro sensitization of RBCs is a two-stage technique referred to as the __.

A

indirect antiglobulin test (IAT)

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14
Q

2 Reagents use in AHG

A

Polyspecific AHG
Monospecific AHG

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15
Q

Regaent that contains anti-IgG and C3D

A

Polyspecific AHG

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16
Q

Reagent that contains only anti-IgG

A

Monospecific AHG

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17
Q

Principles of the Antiglobulin Test:
- Antibody molecules and complement components are __.

A

globulins

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18
Q

AHG reacts with human globulin molecules, either __ or __.

A

bound to RBCs or free in serum

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19
Q

The __ detects in vivo sensitization of RBCs with IgG or complement components.

A

direct antiglobulin test (DAT)

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20
Q

Clinical conditions that can result in in vivo coating of RBCs with antibody or complement are the following:

A

• Hemolytic disease of the fetus and newborn (HDFN)
• Hemolytic transfusion reaction (HTR)
• Autoimmune and drug-induced hemolytic anemia (AIHA).

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21
Q

Principle of Direct AHG

A

Washed Patient RBC (sentisized in vivo) + (coombs’ Sera) AHG Reagent Polyspecific = Visual Red Cell Agglutination

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22
Q

___ is used to demonstrate in vitro reactions between red cells and coating antibodies, as in antibody detection, antibody identification, blood grouping, and compatibility testing.

A

Indirect Antiglobulin Test

23
Q

The IAT is performed to determine in vitro sensitization of RBCs and is used in the following situations:

A

• Detection of incomplete (nonagglutinating) antibodies to potential donor RBCs (compatibility testing) or to screen- ing cells (antibody screen) in serum
• Determination of RBC phenotype using known antisera (e.g., weak D, any other antigen testing that requires IAT)
• Titration of incomplete antibodies

24
Q

Factors Affecting the Antiglobulin Test

A

• Ratio of serum to cells
• Reaction medium
• Temperature
• Incubation time
• Washing of RBCs
• Saline for washing
• Addition of AHG
• Centrifugation for reading

25
Q

True or False.

Increasing the ratio of serum to cells DECREASES the sensitivity of the test system.

A

False.

Increasing the ratio of serum to cells INCREASES the sensitivity of the test system.

26
Q

Ratio of Serum to Cells

A

2 drops of serum and 1 drop of a 5% volume of solute per volume of solution (v/v) suspension of cells

27
Q

Factors Affecting the Antiglobulin Test: Reaction mediums include _, _ and _.

A

albumin, LISS, and polyethylene glycol.

28
Q

The macromolecules of _ allow antibody-coated cells to come into closer contact with each other so that agglutination occurs.

A

albumin

29
Q

In 1965, Stroup and MacIlroy42 reported on the increased _ of the IAT if albumin was incorporated into the reaction medium.

A

sensitivity

30
Q

The use of _ does not seem to provide any advantage over LISS techniques and adds to the COST of the test.

A

albumin

31
Q

_ enhance antibody uptake and allow incubation times to be decreased—from 30 to 60 minutes to 10 to 15 minutes—by reducing the zeta potential surrounding the RBC.

A

Low ionic strength solutions (LISS)

32
Q

(LISS) enhance antibody uptake and allow incubation times to be decreased—from 30 to 60 minutes to __

A

10 to 15 minutes

33
Q

In LISS, Increasing the serum-to-cell ratio increased the ionic strength of the reaction mixture, leading to a _ in sensitivity and counteracting the shortened incubation time of the test.

A

decrease

34
Q

_ is a water-soluble linear polymer and is used as an additive to increase antibody uptake.

A

Polyethylene glycol (PEG)

35
Q

_ is the AHG reagent of choice with PEG testing to avoid false-positive reactions.

A

Anti-IgG

36
Q

_ action is to remove water molecules surrounding the RBC (the water of hydration theory), thereby effectively concentrating antibody.

A

Polyethylene glycol (PEG)

37
Q

Majority of IgG antibodies is optimal at _

A

37˚c

38
Q

For cells suspended in saline, incubation times may vary between _ and _ minutes

A

30 and 120 minutes

39
Q

Incubation time: Significant antibodies can be detected after _ minutes

A

30

40
Q

When both the DAT and IAT are performed, RBCs must be saline-washed a minimum of _ times before adding AHG reagent

A

3

41
Q

Inadequate washing may result in a __ reaction because of neutralization of the AHG reagent by residual unbound serum globulins.

A

false-negative

42
Q

The _ phase of a DAT and IAT is one of the most important steps in testing.

A

washing

43
Q

True or False? Washing should be performed immediately after being removed from the incubator and in as short a time as possible to minimize the elution of low-affinity antibodies.

A

True

44
Q

Centrifugation at each wash should be sufficient to provide a _ cell button and therefore minimize the possible loss of cells with each discard of saline.

A

firm cell button

45
Q

Ideally, the saline used for washing should be _ (suggested open expiration of 30 days)

A

fresh

46
Q

Saline used for washing buffered to a pH of __ to __.

A

7.2 to 7.4.

47
Q

Saline stored for long periods in plastic containers has been shown to _ in pH, which may _ the rate of antibody elution during the washing process, yielding a false-negative result

A

decrease in pH

increase rate of antibody

48
Q

Significant levels of bacterial contamination in saline have been reported; this situation can contribute to _ results.

A

false-positive

49
Q

Addition of AHG
• Should be added _ after washing

A

immediately

50
Q

True or False. Centrifugation of the cell button for reading of hemagglutination along with the method used for resuspending the cells is a crucial step in the technique.

A

True

51
Q

The CBER- recommended method for the evaluation of AHG uses _ relative centrifugal forces (RCFs) for _ seconds

A

1,000 rcf, 20 seconds

52
Q

Inadequate resuspension may cause weak
_ results

A

false-postive

53
Q

Too vigorous may yield _ results

A

false-negative

BB Lab (SF) (2 decks)

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