CLINICAL LAB SCIENEC

426
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
should be cleaned and restored to its former position. Gloves should be discarded
appropriately and the hands washed thoroughly in accordance with
established policies.
Reporting of Results
Interpret your results for ABO direct blood grouping on slides according to the criteria
found at the end of Procedure #2, substituting “slide” for “tube.”
MANUAL IMMUNOHEMATOLOGY PROCEDURE #4
Indirect (Reverse) Grouping by Tube
Principles
The blood groups A, B, and O normally have antibodies against the blood group the
individual does not possess, as described in the direct grouping methodology in Procedure
#2. Therefore, in indirect grouping, the test is for the antibodies and not for the
antigen. The indirect group method is often used to confirm the forward grouping and
should correlate under normal conditions where the patient’s immune system is functioning
normally. The interpretation for an indirect grouping method is opposite that
of the forward grouping. Therefore, antibodies may be used to indicate the reverse
grouping, because, for instance, a group A individual would have antibodies against
group B RBCs.
This procedure describes the tube method and is sometimes called back
grouping. This procedure appears to be the easiest for interpretation, because the
plasma proteins have been removed by washing the RBCs and will not interfere with
the procedure.
Equipment and Supplies
1. Gloves, disposable paper towels, and disinfectant or other cleaning solution
2. Report form
3. A 2% to 5% RBC suspension of washed RBCs from the patient being tested, prepared
following the steps set out in Procedure #1
4. Waterproof sharp marker
5. Normal physiological (0.85%) saline (blood bank quality) in squeeze bottle.
6. Disposable Pasteur pipettes or transfer pipettes
7. Commercially prepared Group A cells (2 – 5% cell suspension)
8. Commercially prepared Group B cells (2 – 5% cell suspension)
9. Disposable 12 × 75 mm test tubes and test tube rack
10. Centrifuge (serofuge) with head that will contain 12 × 75 mm tubes at
2000 rpm
11. Illuminating lamp with magnifying mirror (optional)
12. Disposal containers appropriate for biohazardous waste and sharps container
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