Direct Antiglobulin Test (DAT)

Question 1

Reagent used in DAT and IAT to detect IgG antibodies and complement

Answer 1

Antihuman globulin (AHG) reagent

Question 2

What is an older name for AHG?

Answer 2

Coombs

Question 3

Detects antibodies or complement bound to red cells IN VIVO

Answer 3

Direct Antiglobulin Test (DAT)

Question 4

TRUE or FALSE:
DAT requires an incubation phase

Answer 4

FALSE - DAT doesn’t require an incubation phase

Question 5

Why is IgG called an incomplete or sensitizing antibody?

Answer 5

It’s too small to create visible agglutination without enhancement

Question 6

2 ways IgG antibodies are formed

Answer 6

-Prior transfusion
-Pregnancy

Question 7

__________ is often the first sign the antigen-antibody have attached

Answer 7

Hemolysis

Question 8

Aids in the detection of IgG antibodies and complement that have attached to red cells but have not resulted in visible agglutination

Answer 8

Antihuman Globulin Reagent (AHG)

Question 9

The following are advantages of which type of AHG (polyclonal/monoclonal):
-Inexpensive to produce
-Quick to reproduce
-Higher overall antibody affinity against antigen due to recognition of multiple epitopes
-Offers greater sensitivity for detecting proteins that are present in low quantities

Answer 9

Polyclonal

Question 10

AHG that recognizes multiple epitopes of the same antigen (polyclonal or monoclonal?)

Answer 10

Polyclonal

Question 11

The following are disadvantages of which AHG (polyclonal/monoclonal):
-Variability between different batches manufactured
-Higher potential for cross reactivity due to recognizing multiple epitopes

Answer 11

Polyclonal

Question 12

AHG that only binds with one unique epitope (polyclonal/monoclonal?)

Answer 12

Monoclonal

Question 13

The following are advantages of which AHG (polyclonal/monoclonal):
-Can produce large quantities of identical antibody
-High specificity to a single epitope (reduced risk of cross reactivity)

Answer 13

Monoclonal

Question 14

The following are disadvantages of which AHG (polyclonal/monoclonal):
-Expensive to produce
-More time to develop and produce hybridized clone
-Small change in epitope structure often renders the monoclonal antibody unable to detect target

Answer 14

Monoclonal

Question 15

Reagent that contains both anti-IgG and anti-C3d antibodies

Answer 15

Polyspecific AHG

Question 16

Reagent that is used in the investigation of a positive DAT to determine the nature of the molecules attached to the RBCs

Answer 16

Monospecific AHG

Question 17

A (negative/poitive) DAT is an important indicator of potential immune-mediated RBC destruction in the body

Answer 17

Positive

Question 18

4 causes of a positive DAT

Answer 18

-Transfusion reaction
-Hemolytic Disease of the Newborn (HDN)
-Auto-Immune Hemolytic Anemia (AIHA)
-Drug induced reactions

Question 19

Put in order for DAT testing:
A-Add poly specific AHG and centrifuge
B-Add check cells to any negative reactions
C-Wash patient’s red cells three to four times with saline

Answer 19

C - A - B

Question 20

What is the preferred specimen for blood bank? Why?

Answer 20

EDTA because it chelates calcium which prevents in vitro sensitization

Question 21

What is added to all negative DAT reactions?

Answer 21

Check cells

Question 22

What are check cells?

Answer 22

Group O D positive cells with anti-D (IgI) attached

Question 23

TRUE or FALSE:
Check cells will turn a negative reaction into a positive one. This proves that AHG was added

Answer 23

TRUE

Question 24

A negative reaction after the addition of check cells could mean what? (2)

Answer 24

-AHG was not added
-Cells were not washed adequately

Question 25

This type of testing releases/removes the protein coating the cells and allows the antibody to react with known red cell antigens to specifically identify the antibody

Answer 25

Elution

Question 26

Different ways elution can be accomplished (3)

Answer 26

-Heat
-Change in pH
-Chemicals

Question 27

Best pH range for DAT testing

Answer 27

6.5-7.5

Question 28

Pushes cells closer together

Answer 28

Centrifugation

Question 29

Solution that has fewer (+) ions and more readily allows binding

Answer 29

Low /ionic Strength Solution (LISS)

Question 30

Removes water thereby concentrating the antibody. Good for detecting weak antibodies

Answer 30

Polyethylene Glycol (PEG)