ABO Typing and Discrepancies

Question 1

What is the optimum temperature for reactivity of serum anti-A and anti-B?

Answer 1

4C

Question 2

What would a Bombay individual’s reverse typing look like?

Answer 2

Agglutination with red cell reagent A & B, as well as group O screening cells.

Question 3

What would you do if you see rouleaux when ABO typing?

Answer 3

Wash cells with saline or saline replacement

Question 4

Why might you see rouleaux when ABO typing?

Answer 4

Maybe due to increased serum proteins due to Waldenstrom’s or Multiple Myeloma

Question 5

What are the room temperature or cold reacting antibodies?

Answer 5

H, I, M, N, P1, Lewis

(Hi I May Not Pack Lunch)

Anti-A1 in an A2 or A2B individual

Question 6

What would you do if there are room temperature or cold-reacting antibodies reacting with their corresponding antigens on reverse cells?

Answer 6

“Mini” cold screen or panel (test @ lower temp!)

Question 6

What would you do if there are room temperature or cold-reacting antibodies reacting with their corresponding antigens on reverse cells?

Answer 6

“Mini” cold screen or panel (test @ lower temp!)

Question 7

What could be a discrepancy in an elderly or newborn’s blood typing?
What could you do to resolve this discrepancy?

Answer 7

Reverse typing may show decreased or absent antibody reactivity. In this scenario you would double check the patients age, or you may do a “mini” cold panel (enhances serum Anti-A, Anti-B so that interpretation will agree with cell grouping)

Question 8

If a patient’s blood typing is currently experiencing a discrepancy but needs to be transfused, what blood group should be given?

Answer 8

Group O cells

Question 9

What could be the cause of this discrepancy?

Anti-A: 4+ Anti-B: 4+ A1 cells: 2+ B cells: 0

Answer 9

PATIENT IS TYPE A2B

Front types as AB
Back types as B

First think: Could this person have a subgroup of A?

22% of people have subgroup A2. People who have A2 may produce anti-A1.

Here, a type A2B person is producing anti-A1.

Question 10

What could be the cause of this discrepancy?

Anti-A: 4+ Anti-B: 4+ A1 cells: 2+ B cells: 0

Answer 10

PATIENT IS TYPE A2B

Front types as AB
Back types as B

First think: Could this person have a subgroup of A?

22% of people have subgroup A2. People who have A2 may produce anti-A1.

Here, a type A2B person is producing anti-A1.

Question 11

What could be the cause of this discrepancy?

Anti-A: 0 Anti-B: 0 A1 cells: 0 B cells: 0

Answer 11

PATIENT IS TYPE O BUT IMMUNOCOMPROMISED

Front types as O
Back types as AB

Some people cannot produce enough antibodies (Anti-A1, Anti-B) for the rxn to be visible in back type, such as immunocompromised, elderly, and newborns.

Question 12

What could be the cause of this discrepancy?

Anti-A: 4+ Anti-B: 4+ A1 cells: 2+ B cells: 2+

Answer 12

PATIENT IS TYPE AB WITH COLD AGGLUTININS

Front types as AB
Back types as O

Back type rxn is very weak. This may be due to cold agglutinins.
Type AB person’s serum is reacting weakly with reagent A and B cells. Warming the serum before repeating the back type may eliminate the discrepancy.

Question 13

What could be the cause of this discrepancy?

Anti-A: MF 4+/O Anti-B: 4+/O A1 cells: 0 B cells: 0

Answer 13

PERSON WAS TRANSFUSED WITH TYPE O RBC UNITS

Front types as AB & O
Back types as AB

Front type shows two different cell populations. Type O RBCs are the universal donor, so pts often receive Type O RBCs even if their blood type is different, esp in emergency situations.

Question 14

What could be the cause of this discrepancy?

Anti-A: 4+ Anti-B: 2+ A1 cells: 0 B cells: 4+

Patient has GI issue

Answer 14

PATIENT IS TYPE A. DUE TO GI DISEASE, PT HAS ACQUIRED B-TYPE.

Anti-B reagent reacts weakly with patient cells in front type.
When you see GI involvement and a weak front type rxn with anti-B that does not agree with the back type, think ACQUIRED B.
Gram negative bacteria chops off a piece of the terminal sugar that defines A antigen. This modified sugar resembles B antigen.

This discrepancy disappears once the GI problem is resolved.

Question 15

What could be the cause of this discrepancy?

Anti-A: 4+ Anti-B: 2+ A1 cells: 0 B cells: 4+

Patient has GI issue

Answer 15

PATIENT IS TYPE A. DUE TO GI DISEASE, PT HAS ACQUIRED B-TYPE.

Anti-B reagent reacts weakly with patient cells in front type.
When you see GI involvement and a weak front type rxn with anti-B that does not agree with the back type, think ACQUIRED B.
Gram negative bacteria chops off a piece of the terminal sugar that defines A antigen. This modified sugar resembles B antigen.

This discrepancy disappears once the GI problem is resolved.

Question 16

What would you see in the type for a person that has A2 subtype? What additional tests could you do to confirm this person has A2 subtype?

Answer 16

Would see a weak reaction in A1 reagent cells in the REVERSE type. This is because people who have A2 subgroup have Anti-A1 in their serum. To confirm, you could do an Anti-A1 / D. biflorus which would be NEGATIVE because this lectin reacts with only A1. If you run the serum on an antibody screen it would all be negative, confirming there are no auto/alloantibodies that are causing this reaction.

Question 17

What are four causes of an unexpected reaction in the A1 reagent cells when typing?

Answer 17

1. A patient with A2 subgroup that produces Anti-A1
2. Cold reactive alloantibody
3. Cold reactive autoantibody
4. Pseudoagglutination due to rouleaux

Question 18

What would you see in the type if a patient has a cold alloantibody? What additional tests could you do to confirm this person has this?

Answer 18

Would see an extra reaction in the A1 reagent cells that doesn’t match the front type. To rule out A2 subgroup, test pt serum against D. biflorus, should be POSITIVE reaction because this lectin only reacts with A1 subgroup.

Perform antibody screen. Should see a positive reaction in one of the screening cells in the immediate spin phase.

Question 19

What would you see in the type if a patient has a cold autoantibody? What additional tests could you do to confirm this person has this?

Answer 19

Would see an extra reaction in the A1 reagent cells that doesn’t match the front type. To rule out A2 subgroup, test pt serum against D. biflorus, should be POSITIVE reaction because this lectin only reacts with A1 subgroup.

Perform antibody screen. Should see a positive reaction in ALL/MOST of the screening cells in the immediate spin phase AND positive auto-control.

Question 20

What would you see in the type if a patient has a pseudoagglutination due to roulaeux? What additional tests could you do to confirm this person has this?

Answer 20

Would see an extra reaction in the A1 reagent cells that doesn’t match the front type.

Rouleaux suspected: Look under microscope. Perform SALINE replacement. Should fix it.

To rule out A2 subgroup, test pt serum against D. biflorus, should be POSITIVE reaction because this lectin only reacts with A1 subgroup.

Perform antibody screen. Should see a NEGATIVE reaction in the screening cells, meaning this rxn is not due to allo/autoantibodies.

Question 21

What are possible causes of weak or missing reactions in the FORWARD type?

Answer 21

• Weak ABO subgroups
• Leukemia/malignancy
• Transfusion of Group O RBCs
• Bone marrow transplant

Question 22

What is the purpose of a Mini Cold Panel?

Answer 22

A Mini Cold Panel enhances serum Anti-A and Anti-B rxns when they are expected but not demonstrable using RT temperature readings. It can also identify cold antibodies reacting with other antigns on A1 and B reagent RBCs