Direct Antiglobulin Test (DAT) Flashcards
Reagent used in DAT and IAT to detect IgG antibodies and complement
Antihuman globulin (AHG) reagent
What is an older name for AHG?
Coombs
Detects antibodies or complement bound to red cells IN VIVO
Direct Antiglobulin Test (DAT)
TRUE or FALSE:
DAT requires an incubation phase
FALSE - DAT doesn’t require an incubation phase
Why is IgG called an incomplete or sensitizing antibody?
It’s too small to create visible agglutination without enhancement
2 ways IgG antibodies are formed
-Prior transfusion
-Pregnancy
__________ is often the first sign the antigen-antibody have attached
Hemolysis
Aids in the detection of IgG antibodies and complement that have attached to red cells but have not resulted in visible agglutination
Antihuman Globulin Reagent (AHG)
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
Polyclonal
AHG that recognizes multiple epitopes of the same antigen (polyclonal or monoclonal?)
Polyclonal
The following are disadvantages of which AHG (polyclonal/monoclonal):
-Variability between different batches manufactured
-Higher potential for cross reactivity due to recognizing multiple epitopes
Polyclonal
AHG that only binds with one unique epitope (polyclonal/monoclonal?)
Monoclonal
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)
Monoclonal
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
Monoclonal
Reagent that contains both anti-IgG and anti-C3d antibodies
Polyspecific AHG
Reagent that is used in the investigation of a positive DAT to determine the nature of the molecules attached to the RBCs
Monospecific AHG
A (negative/poitive) DAT is an important indicator of potential immune-mediated RBC destruction in the body
Positive
4 causes of a positive DAT
-Transfusion reaction
-Hemolytic Disease of the Newborn (HDN)
-Auto-Immune Hemolytic Anemia (AIHA)
-Drug induced reactions
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
C - A - B
What is the preferred specimen for blood bank? Why?
EDTA because it chelates calcium which prevents in vitro sensitization
What is added to all negative DAT reactions?
Check cells
What are check cells?
Group O D positive cells with anti-D (IgI) attached
TRUE or FALSE:
Check cells will turn a negative reaction into a positive one. This proves that AHG was added
TRUE
A negative reaction after the addition of check cells could mean what? (2)
-AHG was not added
-Cells were not washed adequately
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
Elution
Different ways elution can be accomplished (3)
-Heat
-Change in pH
-Chemicals
Best pH range for DAT testing
6.5-7.5
Pushes cells closer together
Centrifugation
Solution that has fewer (+) ions and more readily allows binding
Low /ionic Strength Solution (LISS)
Removes water thereby concentrating the antibody. Good for detecting weak antibodies
Polyethylene Glycol (PEG)
