ABO Discrepancies Procedure

ADVENTIST HEALTHCARE LABORATORY SERVICES
SECTION: BLOOD BANK
PROCEDURE#lll
Title:
ABO DISCREPANCIES
ABO DISCREPANCIES
Principle:
A discrepancy exists when the result of red cell tests disagree with that of the serum
tests. When a discrepancy is encountered, it must be resolved. The interpretation is
delayed until testing and resolution is complete. If the clinical condition of the patient
makes it necessary to transfuse before the problem is resolved, only group 0 red cells
of the appropriate Rh type may be issued. If the problem cannot be resolved on site, a
specimen will be sent to the American Red Cross reference lab for resolution.
Procedure:
A.
B.
Initial tests
1.
Repeat front and back grouping on the same sample. Reflex/order
another ABO test in the LIS and result in the LIS.
2.
Wash the patient and/or reagent red cells several times and re-test.
3.
Incubate tests at room temperature or 4C to facilitate detection of weak
antigens or antibodies. An appropriate control (group 0 cells if testing
patient cells or autologous cells if testing patient serum) is needed to rule
out interference of broadly reactive agglutinins.
Discrepancies due to unexpected serum reactions
1
2.
Cold reactive auto-agglutinins (Anti-I, Anti-H)
a.
Warm the serum and reagent red cells to 37C before mixing and
testing.
b.
Re-test with cold autoadsorbed serum.
Anti-A, suspected
a.
Type the patient with Anti-A1 lectin to demonstrate the cells
belong to a non-A1 subgroup.
b.
Test the serum against several examples (preferably three) of A1,
A2 and 0 cells. Agglutination must be seen with all A1 cells and
ADVENTIST HEALTHCARE LABORATORY SERVICES
SECTION: BLOOD BANK
PROCEDURE #1II
Title:
ABO DISCREPANCIES
3
3.
Treat the patient cells with ficin to increase the reaction with anti-A or
anti-B. Enzyme treated 0 cells must be tested in parallel as a control.
4.
Mixed field agglutination may be seen in a patient receiving nonspecific ABO group cells, bone marrow recipients or with
fetal/maternal bleeds. The patient's history is essential in these cases.
5.
Subgroups
Ax -
does not react with human anti-A but will react 1+ - 2+
with anti-A,B. May react with some monoclonal anti-A.
A3 -
presents a mixed field reaction with anti-A and anti-A,B.
Subgroups of B are less common than subgroups of A. The
AABB Technical Manual may be used as a reference in
discerning subgroups.
6.
Acquired antigens
a.
Acquired B phenotype is characterized by serum with strong antiB and red cells agglutinated strongly by anti-A and weakly by antiB.
1)
2)
b.
If acquired B antigen is suspected, check the patient's
diagnosis. It is often associated with carcinoma of the GI
tract.
Test the patient's serum against autologous red cells. The
patient's anti-B will not agglutinate his/her own red cells that
carry the acquired B.
Acquired A-like antigens may be seen in a condition known as
Tn polyagglutination, in which defective synthesis leaves
abnormal antigenic structures on the red cell surface. Group 0
cells that have been Tn-activated behave as if they have an
acquired A antigen. Treat cells with ficin to degrade the
molecule and eliminate reactivity with anti-A.
Reporting results:
1.
All initial reactions are recorded as seen in the LIS per routine procedures, no
interpretation for the ABO group is entered until the discrepancy is resolved.
ADVENTIST HEALTHCARE LABORATORY SERVICES
SECTION: BLOOD BANK
PROCEDURE#111
Title:
ABO DISCREPANCIES
4
2.
Additional testing is recorded on the "ABO Discrepancy Worksheet."
3.
Once resolved, the ABO group is interpreted in the LIS. An exception report
will generate because the front and back type disagree with the logic table
defined in the LIS. Enter a comment on the exception to explain any additional
testing performed.
Notes:
The AABB Technical Manual may be used as a reference for other specialized testing
related to ABO discrepancies.
References:
1.
2.
AABB Technical Manual, 12th edition, 1996.
Standards for Blood Banks and Transfusion Services, AABB, 18th edition, 1997.
ABO DISCREPANCY WORKSHEET
Patient's Name
Med Record #
Date
Backtype at RT
A1 cells
Tech
Backtype at 4C
A2 cells
B cells
Auto
A1 cells
A2 cells
B cells
Auto
Other:
A2 cells
B cells
Auto
Other:
Anti-A,B
Anti-D
Other:
Backtype with 4 drops serum
A1 cells
A2 cells
Backtype at 37C
B cells
Auto
A1 cells
Other:
Saline replacement backtype
A1 cells
A2 cells
B cells
Auto
Other:
Suspected anti-Al (A1 lectin typing of patient is ordered and resulted in LIS)
Patient serum with
#1
#2
#3
Al cells
A2 cells
0 cells
Front type with washed cells
Anti-A
Anti-B
Anti-A,B
Anti-D
Front type at room temp 30 min
Anti-A
Anti-B
Front type at 4C
Anti-A,B
Anti-D
Anti-A
min
Anti-B
Patient
0 cells
ADVENTIST HEALTHCARE LABORATORY SERVICES
WASHINGTON ADVENTIST HOSPITAL
Takoma Park, Maryland

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