Deck 5: The Antiglobulin Test

Question 1

How is a 40:1 ratio of serum to cells prepared for the AHG test?

A) 5 drops of serum + 1 drop of a 5% v/v RBC suspension
B) 1 drop of serum + 1 drop of a 5% v/v RBC suspension
C) 2 drops of serum + 1 drop of a 5% v/v RBC suspension
D) 1 drop of serum + 5 drops of a 5% v/v RBC suspension

Answer 1

C

Question 2

In preparing anti-IgG, how is excess antibody removed for titer adjustment?

A) Elution
B) Adsorption
C) Block titration
D) Dilution

Answer 2

C

Question 3

What effect does a low pH have on a saline AHG test?

A) Enhances antibody elution
B) Enhances the antigen-antibody complex
C) Increases hydrogen bonding
D) Increases bacterial contamination

Answer 3

A

Question 4

Why is incubation omitted in the direct AHG test?

A) Polyspecific AHG contains a higher dose of anti-IgG.
B) Incubation will cause lysis of red blood cells.
C) Incubation elutes complement components from red blood cells.
D) In vivo antigen antibody complex is already formed.

Question 5

An advantage of polyclonal anti-IgG over monoclonal anti-IgG is:

A) AHG produced in rabbits is more specific than AHG produced in mice.
B) polyclonal anti-IgG will recognize IgG variants.
C) polyclonal anti-IgG also has anticomplement activity.
D) polyclonal anti-IgG recognizes only one IgG epitope.

Question 6

Which of the following is consistent with hemolytic disease of the newborn (HDN)?

A) Recipient antibody coating donor red blood cells
B) Maternal antibody coating fetal red blood cells
C) Fetal antibody coating maternal red blood cells
D) Autoantibody coating individual's own red blood cells

Question 7

"Complete" agglutinins that agglutinate red blood cells in saline are of which immunoglobulin class?

A) IgG
B) IgM
C) IgA
D) IgE

Question 8

All of the following are important in evaluating a positive DAT except:

A) patient diagnosis.
B) drug therapy.
C) transfusion history.
D) donation history.

Question 9

What is the incubation time for the IAT when saline is used instead of LISS?

A) 10 minutes
B) 15 minutes
C) 30 minutes
D) 1 hour

Question 10

If not labeled "gamma heavy chain-specific," monospecific anti-IgG may contain antibodies to:

A) immunoglobulin light chains.
B) alpha heavy chains.
C) mu heavy chains.
D) C3d.

Question 11

Most clinically significant blood group antibodies are of which IgG subclasses?

A) IgG₁ and IgG₂
B) IgG₁ and IgG₃
C) IgG₂ and IgG₃
D) IgG₂ and IgG₄

Question 12

At what temperature is the incubation phase of the AHG test?

A) 22°C
B) 37°C
C) 4°C
D) 56°C

Question 13

What is the action of PEG?

A) Reduces ionic strength to allow for faster antibody uptake
B) Its macromolecules allow for closer contact of antibody-coated RBCs
C) Increases the serum-to-cell ratio
D) Removes water molecules, thereby concentrating antibody

Question 14

A patient came in for a routine type and screen prior to surgery. The antibody screen was negative at 37°C and at the AHG phase. Check cells did not produce agglutination often. What is a possible explanation for this result?

A) Dirty glassware
B) Use of positive DAT cells
C) Inadequate washing
D) Overcentrifugation

Question 15

Polyspecific AHG contains:

A) anti-IgG.
B) anti-C3b-C3d.
C) anti-IgG and anti- C3d.
D) anti-IgG and anti-IgM.

Question 16

What do "check cells" contain?

A) A+ red blood cell coated with anti-D
B) Rh(D)+ red blood cells coated with anti-D
C) Rh(D)- red blood cells coated with anti-D
D) B+ red blood cells coated with anti-D

Question 17

The indirect antiglobulin test detects which antigen-antibody reactions?

A) In vivo
B) In vitro
C) Both in vivo and in vitro
D) None of the above

Question 18

The antihuman globulin (AHG) test was discovered in 1945 by whom?

A) Landsteiner
B) Mollison
C) Coombs
D) Sanger

Question 19

What is a possible consequence of incubating tubes too long with LISS when performing the IAT?

A) Increased sensitivity
B) Hemolysis
C) Elution of antibody from red blood cells
D) All of the above

Question 20

Why was anticomplement introduced into AHG sera?

A) Certain clinically significant antibodies demonstrate complement activity.
B) Complement components enhance Kell antibodies.
C) It provides additional information for transfusion reaction workups.
D) All of the above

Question 21

Saline used for blood banking tests should have a pH of .

A) 5.0 to 5.5
B) 6.8 to 7.2
C) 7.2 to 7.4
D) 7.5 to 8.0

Question 22

How would a negative IAT be demonstrated in solid phase methodology?

A) The cells form a monolayer.
B) There is a pellet at the bottom of the well.
C) The well turns orange.
D) Small agglutinins appear at the bottom of the well.

Question 23

Conventional tube testing in AHG testing has one distinct advantage over gel testing. Identify the advantage.

A) Sensitivity
B) Cost
C) Time savings
D) Automation

Question 24

Why is the 37°C reading omitted when using PEG additive?

A) PEG may cause aggregation of RBCs at 37°C.
B) Antibodies detected by PEG do not react at 37°C.
C) Warm-reacting antibodies are not clinically significant.
D) Unwanted reactions due to C3b will be detected at 37°C.

Question 25

What class of antibody can be present in AHG?

A) IgG
B) IgM
C) IgA
D) All of the above

Question 26

In the production of polyspecific AHG, why are IgG and complement antibodies absorbed with A₁, B, and O cells?

A) To eliminate the possibility of prozone
B) To remove heterospecific antibody
C) To eliminate false-negative results
D) To standardize dilutions of antibody

Question 27

An advantage of monoclonal anti-C3 over polyclonal anti-C3 is:

A) with monoclonal anti-C3, the antibody potency can be controlled.
B) contamination with anti-IgG is avoided with anti-C3.
C) with monoclonal anti-C3, antibody to immunoglobulin light chains are eliminated.
D) false-positives caused by cold agglutinins are avoided with anti-C3.

Question 28

All of the following complement proteins can be found on the red blood cell membrane except:

A) C3d
B) C4b
C) C4a
D) C4d

Question 29

What type of globulin does the antiglobulin test detect?

A) IgG alloantibodies
B) IgG autoantibodies
C) C3b complement components
D) All of the above

Question 30

All of the following conditions may produce a positive DAT except:

A) hemolytic disease of the newborn.
B) hemolytic transfusion reaction.
C) lymphoma.
D) drug-induced hemolytic anemia.

Question 31

How many IgG molecules must be present on the red blood cell for a positive IAT to occur?

A) 10
B) 100
C) 50
D) 500

Question 32

What is the purpose of washing cells in the AHG test?

A) To dilute serum
B) To remove all unbound protein
C) To remove all bound protein
D) To exclude a low-affinity antibody

Question 33

Which IgG antibodies are contained in polyspecific AHG?

A) High titer, high avidity
B) High titer, low avidity
C) Chemically modified
D) Those that are pentameric in structure

Question 34

A patient is discovered to have anti-Fy^a in their serum. The medical technologist needs to phenotype the patient's cells for the corresponding antigen. What test is appropriate for phenotyping?

A) Absorption
B) Elution
C) DAT
D) IAT

Question 35

Why are check cells added to all negative reactions in the AHG test?

A) To ensure AHG was not neutralized by free globulin molecules
B) To wash away any unbound antibody
C) To increase the cell-to-serum ratio
D) To bring the antibody closer to the antigen in the test system

Question 36

All of the following statements regarding the AHG test are true except:

A) when washing cells, all saline should be removed completely.
B) centrifugation should provide a firm pellet.
C) incubation time with LISS should be a minimum of 30 minutes.
D) Coombs' control cells should be added to all negative tubes.

Question 37

The inability to determine the of anti-C3b and anti-C3d individually is one of the difficulties with polyclonal reagents.

A) potency
B) titer
C) presence
D) volume

Question 38

Anti-IgG is specific for what part of the IgG molecule?

A) FC fragment
B) Constant region of Fab fragment
C) Hypervariable region of Fab fragment
D) Kappa light chain

Question 39

How is polyclonal antiglobulin serum made?

A) Serum from one human is injected into another human, and an antibody is produced.
B) Human serum is injected into rabbits, and an immune response triggers the production of an antibody.
C) Murine serum is injected into rabbits, and an immune response triggers the production of an antibody.
D) Murine serum is injected into mice, and an immune response triggers the production of an antibody.

Question 40

An antibody screen is performed, and all three tubes are negative after adding AHG. Check cells are added, and the tubes are centrifuged. No agglutination occurs after the addition of check cells. What is the next course of action?

A) Recentrifuging the tubes
B) Adding one drop of control cells
C) Repeating the antibody screen
D) Adding one drop of AHG

Question 41

Which of the following is not a clinical application for a direct antiglobulin test?

A) HDN
B) HTR
C) AIHA
D) Heterophile detection

Question 42

Which of the following antibodies is least likely to bind complement?

A) Jk^a
B) Kell
C) ABO
D) P

Question 43

Why is it important to use polyspecific AHG rather than monospecific?

A) Polyspecific AHG costs less than monospecific AHG.
B) Polyspecific AHG is easier to use than monospecific AHG.
C) Polyspecific AHG is better at detecting IgG antibodies.
D) Polyspecific AHG is less sensitive to IgG antibodies.

Question 44

False-negative results in antihuman globulin testing can be caused by:

A) overcentrifugation.
B) undercentrifugation.
C) cell suspensions that are too weak or too heavy.
D) all of the above.

Question 45

You are performing an IAT, and you are suspicious of the results. It appears there may be a weak alloantibody present. You decide to repeat the test, and at the LISS stage you decide to add an extra two drops of serum to each tube being tested. What can you expect to happen?

A) There would be no effect.
B) The additional serum increases reaction strengths, because more possible antibody is added to the reaction.
C) Sensitivity of the test decreases, because you increased the ionic strength of the mixture.
D) You lowered the zeta potential, thus enhancing your results.

Question 46

What is the optimal temperature for complement activation?

A) 58°C
B) 37°C
C) 4°C
D) 22°C