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ABO Discrepancies

A Blood Group• A1• A2• A3• A int• A m• A x• A lae• A fint• A bantu• A el• A end

B Blood Group• B 3

• B m

• B x

• B el

Anti A1

•A2 •A2B•A3•Ax

•Oh

Anti H

•A1 •A1B

•Oh

•Ah

•Bh

Lectin

• Dolichos biflorus• Ulex eurapeus• Lotous tetragonolobus

• Small-pox• E.coli• Y.pestis • Pneumonia

Microbes

Non Reactive Agglutination

•Rouleaux formation

•Cold Antibody

•Wharton jelly

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)

Cis AB

A

B

B

A

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 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

Let’s practice !

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

4+ 0 4+ 2+ 4+

Subgroup of A

ABO Discrepancies

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:

Thank you