2 ABO BLOOD GROUP SYSTEM Flashcards
(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
B. An A2 person may form anti-A1; an A1 person will not form anti-A1
The group A1 comprises both A1 and A antigens. Anti-A will react with both A1- and A2-positive RBCs. A person who is group A2 may form anti-A1, but an A1 person will not form anti-A1 (which would cause autoagglutination).
(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
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
(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
D. Anti-A, B, and H
A Bombay phenotype individual does not express A, B, or H antigens; therefore, anti-A, -B, and -H are formed. Because a Bombay phenotype individual has three antibodies, the only compatible blood must be from another Bombay phenotype donor.
(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
D. Group A persons
The acquired B phenomenon is only seen in group A persons.
(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
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.
(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
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.
(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
C. Anti-A 4+, anti-B 1+, A1 cells neg, B cells 4+
In forward typing, a 1+ reaction with anti-B is suspicious because of the weak reaction and the normal reverse grouping that appears to be group A. This may be indicative of an acquired antigen. In the case of an acquired B antigen, the reverse grouping is the same for a group A person. Choice A is indicative of group AB; choice B is indicative of a group A who may be immunocompromised. Choice D may be caused by a mistyping or an antibody against antigens on reverse cells.
(8) Which blood group has the least amount of H antigen?
A. A1B
B. A2
C. B
D. A1
A. A1B
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.
(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
B. A or O
A person who is in need of RBC transfusion and is an A2 with anti-A1 can be transfused with A or O cells because the anti-A1 is typically only reactive at room temperature.
(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
A. Wash the cells with warm saline, and autoadsorb the serum at 4°C
These results point to a cold autoantibody. Washing the cells with warm saline may elute the autoantibody, allowing a valid forward type to be performed. The serum should be adsorbed using washed cells until the autocontrol is negative. Then, the adsorbed serum should be used for reverse typing.
(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
B. Incubate at 22°C or 4°C to enhance weak expression
All negative results may be caused by weakened antigens or antibodies. Room temperature or lower incubation temperature may enhance expression of weakened antigens or antibodies.
(12) N-acetyl-D-galactosamine is the immunodominant carbohydrate that reacts with:
A. Arachis hypogaea
B. Salvia sclarea
C. Dolichos biflorus
D. Ulex europeaus
C. Dolichos biflorus
The immunodominant sugar N-acetyl galactosamine confers A antigen specificity when present at the terminus of the type 2 precursor chain on the RBC membrane. Therefore, its presence would cause RBCs to react with anti-A1 lectin, Dolichos biflorus.
(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
C. Immunodeficiency
The transplant recipient is probably taking immunosuppressive medication to increase graft survival. This can contribute to the loss of normal blood group antibodies as well as other types of antibodies.
(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
D. Positive reaction with anti-A,B
Anti-A,B should react positively with group A or B and any subgroup of A or B (with exception of Am). An A1 (not A2) would react with anti-A1 lectin; only an A2 person with anti-A1 would give a positive reaction with A1 cells; an A2 would react more strongly with anti-H than A1.
(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
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.
