1. Jean Purcelli, MT(ASCP)SBB Blood Centers of the Pacific
ABO DISCREPANCIES A
Jean Purcelli, MT(ASCP)SBB
Blood Centers of the Pacific

2. ABO discrepancies occur because of:
Intrinsic problems with the red cells or the serum.
Test related problems—slide vs. tube
Technical errors.

3. Intrinsic red cell problems
Weaker subgroups of A and B or AB such as A2, Ax, A3, A2B and subgroups of B.
Variant A or B genes such as B(A). Must be differentiated from a subgroup of AB.
A patient who has had a bone marrow transplant or an A or B recipient recently transfused with group O red cells.
Weaker subgroups of A and B or AB such as A2, Ax, A3, A2B and subgroups of B.
Variant A or B genes such as B(A). Must be differentiated from a subgroup of AB.
A patient who has had a bone marrow transplant or an A or B recipient recently transfused with group O red cells.

4. Intrinsic red cell problems
Acquired B. Usually associated with infections from GI (gastro-intestinal) bacteria
Polyagglutinable state. The red cells are unexpectedly agglutinated by human source anti-A and Anti-B. Not seen with monoclonal antisera.
Potent cold agglutinins
Acquired B. Usually associated with infections from GI (gastro-intestinal) bacteria
Polyagglutinable state. The red cells are unexpectedly agglutinated by human source anti-A and Anti-B. Not seen with monoclonal antisera.
Potent cold agglutinins
Acquired B. Usually associated with infections from GI (gastro-intestinal) bacteria
Polyagglutinable state. The red cells are unexpectedly agglutinated by human source anti-A and Anti-B. Not seen with monoclonal antisera.
Potent cold agglutinins

5. Intrinsic problems in the serum
Anti- A or –B is not usually detectable until 4-6 months of age. Any reactivity is usually maternal IgG forms of anti-A or –B. A2 or weaker subgroups of A or AB may produce anti-A1. Anti-A1 will react with A1 cells but not A2 or O cells. Allo-antibodies such as anti-M,-N,-P1, Lea or Leb May react at IS (immidiate spin)or RT(room temperature) and react with the A or B cells.

6. Intrinsic problems with the serum
Abnormal concentrations of proteins or infusion with high molecular weight plasma expanders may show aggregation that is difficult to distinguish from true agglutination.
Immunodeficient patient, due to disease or therapy may have decreased levels of anti-A or –B.
Abnormal concentrations of proteins or infusion with high molecular weight plasma expanders may show aggregation that is difficult to distinguish from true agglutination.
Immunodeficient patient, due to disease or therapy may have decreased levels of anti-A or –B.

7. Intrinsic problems with the serum
Infusion of large volumes of compatible but not type specific plasma.
Bone marrow transplants with compatible but dissimilar ABO groups. Example: a group A individual who receives group O marrow will produce circulating O cells, but produce only anti-B in the serum.
Potent cold aggutinins.
Infusion of large volumes of compatible but not type specific plasma.
Bone marrow transplants with compatible but dissimilar ABO groups. Example: a group A individual who receives group O marrow will produce circulating O cells, but produce only anti-B in the serum.
Potent cold aggutinins.

8. ABO discrepancies seen with test related problems
Abnormal proteins, infusion of macromolecular solutions or improperly collected cord blood (contaminated with Wharton’s jelly) may cause false agglutination of cells. This is especially true when the cells are resuspended in serum which is usual for slide typing.
Abnormal proteins, infusion of macromolecular solutions or improperly collected cord blood (contaminated with Wharton’s jelly) may cause false agglutination of cells. This is especially true when the cells are resuspended in serum which is usual for slide typing.

9. Problems with the test system
Serum may contain antibodies to the dyes used to color anti-A and anti-B (USA) which may give false positives with serum-suspended cells in the slide test.
Serum may contain antibodies to the dyes used to color anti-A and anti-B (USA) which may give false positives with serum-suspended cells in the slide test.

10. Resolving AB0 discrepancies
Repeat the tests after washing patient cells and the A and B cells several times.
Analyze the problem:
Unexptected + or unexpected – results?
What is unusual or different?
Do you see spontaneous agglutination?
Repeat the tests after washing patient cells and the A and B cells several times.
Analyze the problem:
Unexptected + or unexpected – results?
What is unusual or different?
Do you see spontaneous agglutination?

11. Resolving ABO discrepancies
If the serum is unexpectedly positive, does the agglutination look like rouleaux? Use saline-replacement technique.
Should you try to prove anti-A1 in an A2 person. Type patient cells with anti-A1 lectin.
Test the serum with screening cells, and another set of A1 and A2 cells.
If the serum is unexpectedly positive, does the agglutination look like rouleaux? Use saline-replacement technique.
Should you try to prove anti-A1 in an A2 person. Type patient cells with anti-A1 lectin.
Test the serum with screening cells, and another set of A1 and A2 cells.

12. Resolving ABO dicrepancies
Is there strong hemolysis in reverse grouping tubes? Add another drop of appropriate cell and centrifuge again.
Is the serum typing unexpectedly negative?
Add several more drops of serum to all reverse grouping tubes, incuding the 3 O screening cells and an auto control. Incubate at RT or colder.
Is there strong hemolysis in reverse grouping tubes? Add another drop of appropriate cell and centrifuge again.
Is the serum typing unexpectedly negative?
Add several more drops of serum to all reverse grouping tubes, incuding the 3 O screening cells and an auto control. Incubate at RT or colder.
Is there strong hemolysis in reverse grouping tubes? Add another drop of appropriate cell and centrifuge again.
Is the serum typing unexpectedly negative?
Add several more drops of serum to all reverse grouping tubes, incuding the 3 O screening cells and an auto control. Incubate at RT or colder.

13. Resolving ABO discrepancies
If the discrepancy cannot be resolved , a patient should be transfused with group O red cells of the appropriate Rh type.
A donor units may not be labelled or released for transfusion and should be discarded.
If the discrepancy cannot be resolved , a patient should be transfused with group O red cells of the appropriate Rh type.
A donor units may not be labelled or released for transfusion and should be discarded.
If the discrepancy cannot be resolved , a patient should be transfused with group O red cells of the appropriate Rh type.
A donor units may not be labelled or released for transfusion and should be discarded.

14. Refer to examples of paper ABO discrepancies
And serological resolution
Refer to examples of paper ABO discrepancies
And serological resolution