CLINICAL LAB SCIENEC

CHAPTER 17: IMMUNOHEMATOLOGY (BLOOD BANKING) 427
Procedure
1. Wash hands and don gloves.
2. Assemble necessary equipment and supplies.
3. Prepare a 2% to 5% RBC suspension of washed
RBCs from the patient being tested following the
steps set out in Procedure #1
4. Label one 12 × 75 mm tubes “A” and label one “B.”
5. Using a Pasteur pipette or transfer pipette, place
two drops of the suspension in each tube.
6. Into tube A, put two drops of commercially prepared
Group A cells.
7. Into tube B, put two drops of commercially prepared
Group A cells.
8. Tap or gently flick each tube with a finger to mix
the cells.
9. Place both tubes into a centrifuge (called a
serofuge in blood banking), and spin for 30 seconds.
10. Gently remove the tubes without shaking and
slightly tilt the tubes while observing for clumping,
called agglutination. An illuminating lamp with magnifying
mirror may be used as an optional practice.
11. Record which tube or tubes show agglutination,
using the following form. Place a plus sign (“+”)
for agglutination into the appropriate blank(s) and
a minus sign (“–“) to indicate no agglutination.
Results
Tube A
Tube B
12. The strength of an immunohematological reaction
is sometimes clinically significant. The reactions
are grades as shown in Figure 17-3
Grading of Agglutination
The degree of red cell agglutination observed in any
blood bank test procedure is significant and should
be recorded. A system of grading is illustrated.
Description Reaction Grade
Button is one or two large
clumps after being dislodged.
Background is clear.
Button breaks into a few
large clumps. Background
is clear.
Button breaks into many
medium-sized clumps.
Background remains clear.
Button breaks into numerous
tiny clumps. Background
becomes cloudy.
A few small, very fine aggregates
barely visible to the naked eye.
No visible clumps or agglutinates.
FIGURE 17-3 Illustration of agglutination of varying
strengths in ABO tube typing.
Source: Delmar/Cengage Learning.
4 ()
3 ()
2 ()
1 ()
w
0 (Neg)
Reporting of Results
Interpret your results for ABO indirect blood grouping according to the following criteria.
Agglutination in Tube B = Group A
Agglutination in Tube A = Group B
No agglutination in Tubes A and B = Group AB
Agglutination in Tubes A or B = Group O
Tube A Tube B
Results – +
Tube A Tube B
Results + –
Tube A Tube B
Results – –
Tube A Tube B
Results + +
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