Chapter 5 The Antiglobulin Test

Question 1

A principle of the anti globulin test is:

Answer 1

AHG reacts with human globulin molecules bound to RBCs or free in serum

Question 2

Ployspecific AHG reagent contains:

Answer 2

Anti-IgG and anti-C3d

Question 3

Monoclonal anti-C3d is:

Answer 3

Derived from one clone of plasma cells

Question 4

Which clinically significant antibody whose detection has been reported in some instances to be dependent on anti complement activity in polyspecific AHG?

Answer 4

Anti-Jk^a

Question 5

After the addition of IgG-coated RBCs ( check cells) to a negative AHG reaction during an antibody screen, a negative result is observed. What is the interpretation?

Answer 5

The antibody screen needs to be repeated

Question 6

RBCs must be washed in saline at least 3X before the addition of AHG reagent to:

Answer 6

Remove traces of free serum globulins

Question 7

An in vitro phenomenon associated with a positive IAT is:

Answer 7

Identification of alloantibody specificity using a panel of reagent RBCs

Question 8

False-positive DAT results are most often associated with:

Answer 8

Use of refrigerated, clotted blood samples in which complement components coat RBCs in vitro.

Question 9

Polyethylene glycol enhances antigen-antibody reactions by:

Answer 9

Concentrating antibody by removing water

Question 10

Solid-phase antibody screening is based on:

Answer 10

Adherence

Question 11

A positive DAT may be found in which of the following situations?

Answer 11

HDN

Question 12

What do Coombs’ control cells consist of?

Answer 12

Type O-positive cells coated with anti-D

Question 13

Which of the following methods requires the use of check cells?

a. LISS
b. Gel
c. Solid-phase
d. Enzyme-linked

Answer 13

a. LISS

Question 14

Which factor can affect AHG testing, yet is uncontrollable in the lab?

Answer 14

Antibody affinity

Question 15

If you had the authority to decide which primary AHG methodology to utilize at your lab, which method would you choose based on the knowledge that the majority of the staff are generalists?

Answer 15

Solid phase or gel

Question 16

A 27 year old group O mother has just given birth to a group A baby girl. Since the mother has IgG anti-A in her plasma, it is likely that the baby is experiencing some in vivo red cell destruction. Which method and tests would be most effective at detecting the anti-A on the baby’s RBCs?

Answer 16

DAT using gel

Question 17

The antihuman globulin test is also known as ?

Answer 17

Coombs’ Test

Question 18

One-stage procedure, detect sensitization in vivo,

Direct AHG

Answer 18

DAT

Question 19

Two-stage procedure , detect sensitization in vitro,

Indirect AHG

Answer 19

IAT

Question 20

“Complete” agglutinins that agglutinate red cells in saline are of which immunoglobulin class?

a) IgG

b) IgM
 	c) IgA
 	d) IgE

Answer 20

b) IgM

Question 21

What type of globulin does the antiglobulin test detect?

a) IgG alloantibodies
b) IgG autoantibodies
c) C3b complement components

    d) all of the above

Answer 21

d) all of the above

Question 22

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 cells
c) Incubation elutes complement components from red cells

d) In vivo antigen-antibody complex is already formed

Answer 22

d) In vivo antigen-antibody complex is already

Question 23

What do “check cells” contain?

a) A+ red cell coated with anti-D

    b) Rh (D)+ red cells coated with anti-D
 	c) Rh (D)- red cells coated with anti-D
 	d) B+ red cells coated with anti-D

Answer 23

b) Rh (D)+ red cells coated with anti-D

Question 24

Why does anti-C3d activity require standardization in AHG reagents?

Answer 24

high activity will fix anti-I and other clinically insignificant antibodies

Question 25

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

Answer 25

donation history

Question 26

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

Answer 26

7.2 to 7.4

Question 27

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

Answer 27

Fc fragment

Question 28

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

Answer 28

The antibody potency can be controlled

Question 29

What is the action of PEG?

Answer 29

removes water molecules, thereby concentrating antibody

Question 30

``` Direct (DAT) 1-detects 2-specimen 3-incubation 4-application 5-false (+) 6-false (-) ```

Answer 30

``` 1-In vivo sensitization of RBCs by IgG ab 2-EDTA red cells preferred 3-none 4-HDFN,tf rxn, autoimmune hemolytic anemia, drug induced hemolytic anemia 5-complement binding in vitro if RBCs are taken from red-top tube and broad spectrum AHG used -Septicemia -Contamination-Wharton's jelly in cord blood -over reading -over centrifuge 6-test interuption -contamination -improper storage -outdating of AHG -failure to add AHG -inadequate washing -over/under centrifuge ```

Question 31

``` Indirect (IAT) 1-detects 2-specimen 3-incubation 4-application 5-false (+) 6-false (-) ```

Answer 31

1-In vitro sensitization of RBCs by IgG ab 2-serum,plasma,RBCs 3-Serum or plasma with reagent RBCs or RBCs with reagent antiserum 4-Ab screen, Xmatch, RBC phenotyping, weak D testing 5-Cells with pos DAT -over-centrifugation 6-Same as DAT, plus over/under incubation