Hello ABO Discrepancies A Blood Group A 1

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ABO Discrepancies

• • • A Blood Group A 1 A 2 A 3 A int Am Ax A lae A fint A bantu A el A end

• B 3 B Blood Group • Bm • Bx • B el

Anti A 1 • A 2 B • A 3 • Ax • Oh

Anti H • A 1 B • Oh • Ah • Bh

Lectin • Dolichos biflorus • Ulex eurapeus • Lotous tetragonolobus • • Microbes Small-pox E. coli Y. pestis Pneumonia

Non Reactive Agglutination • Rouleaux formation • Cold Antibody • Wharton jelly

Acquired B cell • Limited mainly to Group A 1 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 Bacterial enzyme removes acetyl group Acquired B Phenotype Galactosamine now resembles Dgalactose (found in Group B)

Cis AB 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 A 1 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 A 1 Cell 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 A 1 Cell B Cell O Cell Auto 4+ 4+ 0 0

Example 1 Anti-A Anti-B A 1 Cells B Cells 3+ 0 0 1+ Problem: Causes: Resolution:

Example 2 Anti-A Anti-B A 1 Cells B Cells 3+ 1+ 0 4+ Problem: Causes: Resolution:

Example 3 Anti-A Anti-B A 1 Cells B Cells 2+ 0+ 1+ 4+ Problem: Causes: Resolution:

Example 4 Anti-A Anti-B A 1 Cells B Cells 0 2+mf 3+ 0 Problem: Causes: Resolution:

Example 5 Anti-A Anti-B A 1 Cells B Cells 0 0 Problem: Causes: Resolution:

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