Blood bank 4.2 ABO Blood Group System

Question 1

1. Which of the following distinguishes the A1 blood group from the A2 blood group?

A. A2 antigen will not react with anti-A, A1 will react strongly (4+)
B. An A2 person may form anti-A1; an A1 person will not form anti-A1
C. An A1 person may form anti-A2, an A2 person will not form anti-A1
D. A2 antigen will not react with anti-A from a nonimmunized donor; A1 will react with any anti-A

Answer 1

B. An A2 person may form anti-A1; an A1 person will not form anti-A1

Question 2

2. A patient’s serum is incompatible with O cells. The patient RBCs give a negative reaction to anti-H lectin. What is the most likely cause of these results?
   A. The patient may be a subgroup of A
   B. The patient may have an immunodeficiency
   C. The patient may be a Bombay phenotype individual
   D. The patient may have developed alloantibodies

Answer 2

C. The patient may be a Bombay phenotype individual

Bombay phenotype is the only ABO phenotype incompatible with O cells. The RBCs of a Bombay phenotype individual show a negative reaction to anti-H because the cells contain no H substance.

Question 3

3. What antibodies are formed by a Bombay phenotype individual?
   A. Anti-A and anti-B
   B. Anti-H
   C. Anti-A,B
   D. Anti-A, B, and H

Answer 3

D. Anti-A, B, and H

Question 4

4. Acquired B antigens have been found in:
   A. Bombay phenotype individuals
   B. Group O persons
   C. Persons of all blood groups
   D. Group A persons

Answer 4

D. Group A persons

Question 5

5. Blood is crossmatched on an A-positive person with a negative antibody screen. The patient received a transfusion of A-positive RBCs 3 years ago. The donors chosen for crossmatching were A-positive. Crossmatching was run on the automated analyzer and yielded 3+ incompatibility. How can these results be explained?
   A. The patient has an antibody to a low-frequency antigen
   B. The patient has an antibody to a high-frequency antigen
   C. The patient is an A2 with anti-A1
   D. The patient is an A1 with anti-A2

Answer 5

C. The patient is an A2 with anti-A1

The patient is likely an A2 with anti-A1, which is causing reactivity in the crossmatching. A negative antibody screen rules out the possibility of an antibody to a high-frequency antigen, and two donor units incompatible rules out an antibody to a low-frequency antigen.

Question 6

6. A patient’s RBCs forward as group O, serum agglutinates B cells (4+) only. Your next step would be:

A. Extend reverse typing for 15 minutes
B. Perform an antibody screen, including room-temperature incubation
C. Incubate washed RBCs with anti-A1 and anti-A,B for 30 minutes at room temperature
D. Test patient’s RBCs with Dolichos biflorus

Answer 6

C. Incubate washed RBCs with anti-A1 and anti-A,B for 30 minutes at room temperature

The strong 4+ reaction in reverse grouping suggests the discrepancy is in forward grouping. Incubating washed RBCs at room temperature with anti-A and anti-A,B will enhance reactions.

Question 7

7. Which typing results are most likely to occur when a patient has an acquired B antigen?

A. Anti-A 4+, anti-B-3+, A1 cells neg, B cells neg
B. Anti-A 3+, anti-B neg, A1 cells neg, B cells neg
C. Anti-A 4+, anti-B 1+, A1 cells neg, B cells 4+
D. Anti-A 4+, anti-B 4+, A1 cells 2+, B cells neg

Answer 7

C. Anti-A 4+, anti-B 1+, A1 cells neg, B cells 4+

Question 8

8. Which blood group has the least amount of H antigen?
   A. A1,B
   B. A2
   C. B
   D. A1

Answer 8

A. A1,B

The A1B blood group has the least amount of H antigen. This occurs because both A and B epitopes are present on RBCs, compromising the availability of H epitopes. A1B cells will yield weak reactions with anti-H lectin.

Question 9

9. What type RBCs can be transfused to an A2 person with anti-A1?
   A. A only
   B. A or O
   C. B
   D. AB

Answer 9

B. A or O

Question 10

10. What should be done if all forward and reverse ABO results as well as the autocontrol are positive?
    A. Wash the cells with warm saline, and autoadsorb the serum at 4°C
    B. Retype the sample using a different lot number of reagents
    C. Use polyclonal typing reagents
    D. Report the sample as group AB

Answer 10

A. Wash the cells with warm saline, and autoadsorb the serum at 4°C

Question 11

11. What should be done if all forward and reverse ABO results are negative?
    A. Perform additional testing, such as typing with anti-A1 lectin and anti-A,B
    B. Incubate at 22°C or 4°C to enhance weak expression
    C. Repeat the test with new reagents
    D. Run an antibody identification panel

Answer 11

B. Incubate at 22°C or 4°C to enhance weak expression

Question 12

12. N-acetyl-D-galactosamine is the immunodominant carbohydrate that reacts with:
    A. Arachis hypogaea
    B. Salvia sclarea
    C. Dolichos biflorus
    D. Ulex europeaus

Answer 12

C. Dolichos biflorus

Question 13

13. A stem cell transplant recipient was retyped when she was transferred from another hospital. What is the most likely cause of the following results?
    Patient cells:
    Anti-A: neg
    Anti-B: 4+
    Patient serum:
    A1 cells: neg
    B cells: neg

A. Viral infection
B. Alloantibodies
C. Immunodeficiency
D. Autoimmune hemolytic anemia

Answer 13

C. Immunodeficiency

Question 14

14. What reaction would be the same for an A1 and an A2 person?
    A. Positive reaction with anti-A1 lectin
    B. Positive reaction with A1 cells
    C. Equal reaction with anti-H
    D. Positive reaction with anti-A,B

Answer 14

D. Positive reaction with anti-A,B

Question 15

15. A female patient at 28 weeks’ pregnancy yields the following results:
    Patient cells:
    Anti-A: 3+
    Anti-B: 4+
    Patient serum:
    A1 cells: neg
    B cells: 1+
    O cells: 1+
    Which of the following could be causing the ABO discrepancy?

A. Hypogammaglobulinemia
B. Alloantibody in patient serum
C. Acquired B
D. Weak subgroup

Answer 15

B. Alloantibody in patient serum

The patient is most likely an AB person who has formed a cold-reacting alloantibody reacting with B cells and O cells. An identification panel should be performed. An acquired B person or someone with hypogammaglobulinemia should not make antibody that would agglutinate O cells.

Question 16

16. Which condition would most likely be responsible for the following typing results?
    Patient cells:
    Anti-A: neg
    Anti-B: neg
    Patient serum:
    A1 cells: neg
    B cells: 4+

A. Immunodeficiency
B. Masking of antigens by the presence of massive amounts of antibody
C. Weak or excessive antigen(s)
D. Impossible to determine

Answer 16

C. Weak or excessive antigen(s)

Excessive A substance, as may be found in some types of tumors, may be neutralizing anti-A. Weak A subgroups may fail to react with anti-A and require additional testing techniques (e.g., room-temperature incubation) before their expression is apparent.

Question 17

17. Which of the following results is most likely discrepant?
    Anti-A: neg
    Anti-B: 4+
    A1 cells: neg
    B cells: neg

A. Negative B cells
B. Positive reaction with anti-B
C. Negative A1 cells
D. No problem with this typing

Answer 17

C. Negative A1 cells

Question 18

18. A 61-year-old male with a history of multiple myeloma underwent stem cell transplantation 3 years ago. The donor was O positive, and the recipient was B positive. The patient is admitted to a community hospital for fatigue and nausea. Typing results reveal the following:
    Anti-A = 0
    Anti-B =0
    Anti-A,B = 0
    Anti-D = 4+
    A1 cells = 4+
    B cells = 0
    How would you report this type?

A. O positive
B. B positive
C. A positive
D. Undetermined

Answer 18

D. Undetermined

In a transplantation scenario, there are no methods to employ to solve the discrepancy. The medical laboratory scientist must rely on the patient history of donor type and recipient type and the present serological picture. Giving a B-positive recipient an O-positive transplant constitutes a minor ABO mismatch. The forward type resembles the donor. The reverse type still resembles the recipient. The ABO type reported out does not fit a pattern resulting in an undetermined type.