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Lectin
• Dolichos biflorus• Ulex eurapeus• Lotous tetragonolobus
• Small-pox• E.coli• Y.pestis • Pneumonia
Microbes
Acquired B cell
• Limited mainly to Group A1 individuals with:– 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
Acquired B Phenotype
Bacterial enzyme removes acetyl group
Galactosamine now resembles D-
galactose (found in Group B)
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 20-24 ˚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
Initial hypothesis:
Forward: Group O Rh Positive
Reverse: Group B
ABO discrepancy is an unexpected antibody reaction withAI cells.
Case study 1
Resolution:All tubes are reverified for positive identification. No errors arefound.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.
Initial hypothesis:
Forward: Group A Rh Positive
Reverse: Group AB
ABO discrepancy is a missing antibody.
Case study 2
Resolution:All tubes are reverified for positive identification. No errors arefound.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 antibodyscreening cells.
The negative auto control indicates that no autoantibody is present atroom temperature, or 4ᵒ C. The negative screening cells indicate that nocold-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 antiglobulintest (DAT) whenever the AB typing is determined, a DAT is performed.
Anti-A Anti-B Anti-AB A1Cell B Cell O Cell Auto
Polyclonal antiserum 1+ 1+ 1+ 4+ 4+ 0 0
Monoclonal antiserum 0 0 0
Polyagglutination
ABO Discrepancies
Example 1
Anti-AAnti-A Anti-BAnti-B A1 CellsA1 Cells B CellsB Cells
3+3+ 00 00 1+1+
Problem:
Causes:
Resolution:
Example 2
Anti-AAnti-A Anti-BAnti-B A1 CellsA1 Cells B CellsB Cells
3+3+ 1+1+ 00 4+4+
Problem:
Causes:
Resolution:
Example 3
Anti-AAnti-A Anti-BAnti-B A1 CellsA1 Cells B CellsB Cells
2+2+ 0+0+ 1+1+ 4+4+
Problem:
Causes:
Resolution:
Example 4
Anti-AAnti-A Anti-BAnti-B A1 CellsA1 Cells B CellsB Cells
00 2+mf2+mf 3+3+ 00
Problem:
Causes:
Resolution:
Example 5
Anti-AAnti-A Anti-BAnti-B A1 CellsA1 Cells B CellsB Cells
00 00 00 00
Problem:
Causes:
Resolution: