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ABO
Discrepancies
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A Blood Group
A1
A2
A3
A int
Am
Ax
A lae
A fint
A bantu
A el
A end
B Blood Group
•B3
•Bm
•Bx
• B el
Anti A1
• A2
• A2B
• A3
• Ax
• Oh
Anti H
• A1
• A1B
• Oh
• Ah
• Bh
Lectin
• Dolichos biflorus
• Ulex eurapeus
• Lotous tetragonolobus
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Microbes
Small-pox
E.coli
Y.pestis
Pneumonia
Non Reactive Agglutination
• Rouleaux formation
• Cold Antibody
• Wharton jelly
Acquired B cell
• Limited mainly to Group
A1 individuals with:
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Lower GI tract disease
Cancer of colon/rectum
Intestinal obstruction
Gram negative septicemia
(i.e. E. coli)
Acquired B
• Bacteria (E. coli) have a deacetylating
enzyme that effects the A sugar….
Group A
individual
N-acetyl galactosamine
Bacterial enzyme removes
acetyl group
Acquired B
Phenotype
Galactosamine now
resembles Dgalactose (found in
Group B)
Cis AB
A
B
A
B
Secretary Substance
• Stomach carcinoma
• Pancreatic carcinoma
• Ovarian carcinoma
B(A) phenotype
• Similar to acquired B
• Patient is Group B with an apparent extra
A antigen
• The B gene transfers small amounts of the
A sugar to the H antigen
• Sometimes certain anti-A reagents will
detect these trace amount of A antigen
• Resolution: test with another anti-A
reagent from another manufacturer
False Negative Results in ABO
Testing
• Reagent or test serum not added to a tube
• Hemolysis not identified as a positive
reaction
• Inappropriate ratio of serum ( or reagent )
to red cells
• Tests not centrifuged sufficiently
• Tests incubated at temperatures above 2024 ˚C
• Incorrect interpretation or recording of
test results
False Positive Results in ABO
Testing
• Over centrifugation of tubes
• Use of contaminated reagents,
red cells, or saline
• Use of dirty glassware
• Incorrect interpretation or
recording of test results
Let’s practice !
Case study 1
Initial hypothesis:
Forward: Group O Rh Positive
Reverse: Group B
ABO discrepancy is an unexpected antibody
reaction with
AI cells.
Resolution:
All tubes are reverified for positive
identification. No errors are
found.
A new sample is requested to investigate the
potential of a mislabeled sample.
All testing is repeated. The results are the same.
History:
She was crossmatched 5 years ago and was typed
as B positive.
She was the recipient of a bone marrowtransplant
due to aplastic anemia.
The donor was a group 0, D-positive sibling.
Case study 2
Initial hypothesis:
Forward: Group A Rh Positive
Reverse: Group AB
ABO discrepancy is a missing antibody.
Resolution:
All tubes are reverified for positive identification. No errors are
found.
A new sample is requested to investigate the potential of a mislabeled sample.
All testing is repeated. The results are the same.
History:
Patient is 95 years old and has decreased production of anti-B due to her age.
To prove this theory, room temperature incubation at 4ᵒ C for 10 minutes is
performed
testing the patient's serum against A1 and B cells, an auto control, and
antibody
screening cells.
The negative auto control indicates that no autoantibody is present at
room temperature, or 4ᵒ C. The negative screening cells indicate that no
cold-reactive alloantibody is present in the sample.
The patient's ABO type is group A.
Case study 3
Initial hypothesis:
Forward: Group AB Rh Positive
Reverse: Group AB
No ABO discrepancy
Because the manufacturer's insert requires the performance of a direct
antiglobulin
test (DAT) whenever the AB typing is determined, a DAT is performed.
ABO Discrepancies
Anti-A
Anti-B
Anti-AB
A1Cell
B Cell
4+
0
4+
2+
4+
Subgroup of A
ABO Discrepancies
Anti-A Anti-B Anti-AB
Polyclonal
antiserum
1+
1+
1+
Monoclonal
antiserum
0
0
0
Polyagglutination
A1Cell
B Cell
O Cell
Auto
4+
4+
0
0
Example 1
Anti-A
Anti-B
A1 Cells
B Cells
3+
0
0
1+
Problem:
Causes:
Resolution:
Example 2
Anti-A
Anti-B
A1 Cells
B Cells
3+
1+
0
4+
Problem:
Causes:
Resolution:
Example 3
Anti-A
Anti-B
A1 Cells
B Cells
2+
0+
1+
4+
Problem:
Causes:
Resolution:
Example 4
Anti-A
Anti-B
A1 Cells
B Cells
0
2+mf
3+
0
Problem:
Causes:
Resolution:
Example 5
Anti-A
Anti-B
A1 Cells
B Cells
0
0
0
0
Problem:
Causes:
Resolution:
Thank you