Comparing Blood Bank Methodologies Flashcards
What does a negative reaction look like?
Tube:
Gel:
Solid Phase:
Tube: no agglutination
Gel: cells at pellet at bottom of column
Solid Phase: cells in solid pellet in well
What is the volume of plasma required for each?
Tube:
Gel:
Solid Phase:
Tube: 100 ul
Gel: 25 ul
Solid Phase: 50 ul
Volume of plasma required for each?
Tube: 3%
Gel: 0.8%
Solid Phase: 3%
Tests for IgG, IgM, or both?
Tube: gG & IgM (IS & IAT phases)
Gel: Designed for IgG. IgM
may be detected due to
size of IgM molecule
Solid Phase: Designed for IgG
Includes incubation at 37 degrees Celsius?
Tube: yes
Gel: yes
Solid Phase: yes
Includes a wash step?
Tube: yes
Gel: no
Solid Phase: yes
utilizes centrifugation?
all three
What is the advantage of tube testing?
Gold standard,
testing
conditions
easily
manipulated,
differentiates
IgG from IgM
What are the advantages of gel?
Small sample
volume, not as
subjective of
grading, very
sensitive, can
be automated
What are the advantages of solid phase?
Can be
automated,
sensitive
What are the disadvantages of tube testing?
Requires competence
of techs, tech time, subjective scoring
What are the disadvantages of gel?
Very sensitive,
rouleaux
interferes as
there isn’t a wash step,
requires 0.8%
RBCsuspension
What are the disadvantages of solid phase?
Subjective
grading
Direct agglutination…
o Antibody + RBC = visible agglutination
o “Immediate spin” phase
o IgM or cold-reacting IgG
Indirect Antiglobulin Test (IAT)…
o Antibody + RBC
o Incubation at 37C (antibody coats RBCs)
o Wash (remove unbound antibody)
o Add anti-human IgG (antibody to Fc portion of human IgG)
o Visible agglutination
o Detection of IgG antibody
Gel Testing:
Relies on antibody-coated red cells getting stuck in gel matrix containing anti-____
IgG
gel testing…
Relies on antibody-coated red cells getting stuck in gel matrix containing anti-IgG
Antibody + RBCs in upper chamber, incubation at 37C
Centrifugation
RBCs fall through gel matrix containing anti-IgG
Antibody-coated cells get stuck in matrix/cells not coated fall to the bottom of column
Designed to detect IgG
- In tube testing, which of the following best describes the difference between the immediate spin (IS) phase and the IAT phase?
a. IS phase usually detects warm reacting antibody; IAT phase usually detects cold reacting
antibody
b. IS phase usually detects IgM; IAT phase usually detects IgG
c. IS phase may indicate clinically significant reactivity; IAT phase often indicates
insignificant reactivity
d. IS phase detects alloantibody; IAT phase detects autoantibody
b. IS phase usually detects IgM; IAT phase usually detects IgG
- Which of the following best represents sample volume requirements for each methodology?
a. Gel>Solid phase>Tube
b. Tube>Solid phase>Gel
c. Solid phase>Gel>Tube
d. Solid phase>Tube>Gel
b. Tube>Solid phase>Gel
- Which of the following is an important disadvantage of gel testing?
a. Cannot be automated
b. Requires large sample volume
c. Very subjective reaction grading
d. Rouleaux can interfere with detection of IgG antibody
d. Rouleaux can interfere with detection of IgG antibody
What does SPRCA stand for?
solid phase red cell adherence assay
Antigens coat microwells
Plasma and enhancement is added to wells, incubated at 37C,
antibodies (if present) attach to antigens
Wash step: unbound antibody is removed
Indicator cells (RBCs bound to anti-IgG) are added
Centrifugation
Interpretation: a tight cell button indicates a negative reaction,
effacement of the cell button indicates a positive reaction
Solid Phase Testing
