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2. ABO Discrepancies

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

4. B Blood Group • B 3 • B m • B x • B el

5. Anti A1 • A2 • A2B • A3 • Ax • Oh

6. Anti H • A1 • A1B • Oh • Ah • Bh

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

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

9. 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)

10. Acquired B • Bacteria (E. coli) have a deacetylating enzyme that effects the A sugar…. Acquired B Phenotype Group A individual N-acetyl galactosamine Galactosamine now resembles D-galactose (found in Group B) Bacterial enzyme removes acetyl group

11. Cis AB A B A B

12. Secretary Substance • Stomach carcinoma • Pancreatic carcinoma • Ovarian carcinoma

13. 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

14. 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

15. 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

16. Let’s practice !

19. Case study 1 Initial hypothesis: Forward: Group O Rh Positive Reverse: Group B ABO discrepancy is an unexpected antibody reaction with AI cells.

20. 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.

21. Case study 2 Initial hypothesis: Forward: Group A Rh Positive Reverse: Group AB ABO discrepancy is a missing antibody.

22. 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.

23. 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.

24. ABO Discrepancies Subgroup of A

25. ABO Discrepancies Polyagglutination

26. Example 1 Problem: Causes: Resolution:

27. Example 2 Problem: Causes: Resolution:

28. Example 3 Problem: Causes: Resolution:

29. Example 4 Problem: Causes: Resolution:

30. Example 5 Problem: Causes: Resolution:

35. Thank you