Comparing Blood Bank Methodologies

Question 1

What does a negative reaction look like?

Tube:
Gel:
Solid Phase:

Answer 1

Tube: no agglutination

Gel: cells at pellet at bottom of column

Solid Phase: cells in solid pellet in well

Question 2

What is the volume of plasma required for each?

Tube:
Gel:
Solid Phase:

Answer 2

Tube: 100 ul
Gel: 25 ul
Solid Phase: 50 ul

Question 3

Volume of plasma required for each?

Answer 3

Tube: 3%
Gel: 0.8%
Solid Phase: 3%

Question 4

Tests for IgG, IgM, or both?

Answer 4

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

Question 5

Includes incubation at 37 degrees Celsius?

Answer 5

Tube: yes
Gel: yes
Solid Phase: yes

Question 6

Includes a wash step?

Answer 6

Tube: yes
Gel: no
Solid Phase: yes

Question 7

utilizes centrifugation?

Answer 7

all three

Question 8

What is the advantage of tube testing?

Answer 8

Gold standard,
testing
conditions
easily
manipulated,
differentiates
IgG from IgM

Question 9

What are the advantages of gel?

Answer 9

Small sample
volume, not as
subjective of
grading, very
sensitive, can
be automated

Question 10

What are the advantages of solid phase?

Answer 10

Can be
automated,
sensitive

Question 11

What are the disadvantages of tube testing?

Answer 11

Requires competence
of techs, tech time, subjective scoring

Question 12

What are the disadvantages of gel?

Answer 12

Very sensitive,
rouleaux
interferes as
there isn’t a wash step,
requires 0.8%
RBCsuspension

Question 13

What are the disadvantages of solid phase?

Answer 13

Subjective
grading

Question 14

Direct agglutination…

Answer 14

o Antibody + RBC = visible agglutination
o “Immediate spin” phase
o IgM or cold-reacting IgG

Question 15

Indirect Antiglobulin Test (IAT)…

Answer 15

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

Question 16

Gel Testing:
 Relies on antibody-coated red cells getting stuck in gel matrix containing anti-____

Answer 16

IgG

Question 17

gel testing…

Answer 17

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

Question 18

1. 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

Answer 18

b. IS phase usually detects IgM; IAT phase usually detects IgG

Question 19

2. 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

Answer 19

b. Tube>Solid phase>Gel

Question 20

3. 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

Answer 20

d. Rouleaux can interfere with detection of IgG antibody

Question 21

What does SPRCA stand for?

Answer 21

solid phase red cell adherence assay

Question 22

 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

Answer 22

Solid Phase Testing