Results: anti-A 0, anti-B 0; A1 cells 4+, B cells 4+. Group O screening cells and the autocontrol are both 2+ at room temperature. The best next step is:

Repeat the reverse grouping with cold-autoadsorbed plasma

Type the cells with anti-H lectin for Bombay

Report group O and issue group O plasma

Repeat the forward grouping with anti-A1 lectin

An 88-year-old patient types: anti-A 4+, anti-B 0; A1 cells 0, B cells 0. The antibody screen is negative. What is the best next step?

Incubate the reverse tubes at room temperature for 15 to 30 minutes

Test the plasma with anti-A1 lectin

Wash the cells and repeat the forward grouping

Antigens: ABO

12 ASCP MLS practice questions on Antigens: ABO, part of Blood Banking. The first 12 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
Results: anti-A 0, anti-B 0; A1 cells 4+, B cells 4+. Group O screening cells and the autocontrol are both 2+ at room temperature. The best next step is:
1. ARepeat the reverse grouping with cold-autoadsorbed plasma
2. BType the cells with anti-H lectin for Bombay
3. CReport group O and issue group O plasma
4. DRepeat the forward grouping with anti-A1 lectin
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Answer: A · Repeat the reverse grouping with cold-autoadsorbed plasma
The positive autocontrol points to a cold autoantibody, often anti-I, reacting with every cell at room temperature. Removing it by autoadsorption in the cold lets the reverse grouping be read clearly. A Bombay phenotype would give a negative autocontrol, because the patient's own cells lack H. The patient appears to be group O, but this is confirmed after the interference is removed.
- B: A Bombay patient's anti-H does not react with their own H-negative cells, so the autocontrol would be negative.
- C: The ABO discrepancy should be resolved before reporting.
- D: The forward grouping is not in doubt here.
Question 2 · Medium
Ulex europaeus lectin (anti-H) is tested against red cells of several ABO groups. It reacts most strongly with cells of group:
1. AA1B
2. BO
3. CB
4. DA1
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Answer: B · O
Group O people have no active A or B transferase, so their H antigen is not converted. H antigen falls roughly in the order O > A2 > B > A2B > A1 > A1B. Ulex europaeus lectin (anti-H) therefore reacts most strongly with group O cells. A1 and A1B people may have so little H that they can make weak anti-H.
- A: A1B cells have the least H, because both transferases use it.
- C: Group B cells convert a good part of their H antigen to B.
- D: A1 cells convert most of their H antigen to A.
Question 3 · Easy
The sugar that gives the A antigen its specificity is:
1. AN-acetylgalactosamine
2. BL-fucose
3. CN-acetylglucosamine
4. DD-galactose
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Answer: A · N-acetylgalactosamine
The A gene's transferase adds N-acetylgalactosamine to the H antigen, and this terminal sugar defines A specificity. The B transferase adds D-galactose instead. L-fucose is the sugar that makes H antigen from its precursor chain. Dolichos biflorus lectin binds N-acetylgalactosamine on A1 cells.
- B: L-fucose defines the H antigen, the precursor of A and B.
- C: N-acetylglucosamine is part of the precursor chain, not the A determinant.
- D: D-galactose is the sugar that defines the B antigen.
Question 4 · Hard
A patient with no history of transfusion or transplant shows mixed-field agglutination with anti-A and anti-A,B, and has anti-B in the plasma. The most likely subgroup is:
1. AA3
2. BAel
3. CA1
4. DAx
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Answer: A · A3
A3 cells give a typical mixed-field pattern with anti-A and anti-A,B: small agglutinates in a sea of free cells. A recent transfusion or transplant can look the same, which is why the history matters. Ax cells react weakly or not at all with anti-A but better with anti-A,B. Ael cells are not agglutinated at all and are shown only by adsorption and elution.
- B: Ael cells are not agglutinated by anti-A.
- C: A1 cells react strongly and evenly with anti-A.
- D: Ax cells usually react better with anti-A,B than with anti-A, not in a mixed field.
Question 5 · Hard
An 88-year-old patient types: anti-A 4+, anti-B 0; A1 cells 0, B cells 0. The antibody screen is negative. What is the best next step?
1. ATest the plasma with anti-A1 lectin
2. BIncubate the reverse tubes at room temperature for 15 to 30 minutes
3. CWash the cells and repeat the forward grouping
4. DReport the patient as group A
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Answer: B · Incubate the reverse tubes at room temperature for 15 to 30 minutes
The expected anti-B is missing, which is common in elderly people, infants and immunodeficient patients. Incubating the reverse grouping at room temperature, or at 4 °C with an autocontrol and group O cells, can bring up weak antibodies. The discrepancy must be resolved before the group is reported. If blood is needed meanwhile, group O red cells are given.
- A: Lectins are used on red cells, not on plasma.
- C: The forward grouping is clear; the problem is in the reverse grouping.
- D: The group cannot be reported until the reverse grouping agrees.
Question 6 · Medium
In ABO grouping, anti-A,B reagent is mainly useful because it:
1. ASeparates A1 cells from A2 cells
2. BDetects weak A subgroups such as Ax
3. CDetects anti-A1 in the plasma
4. DDetects the Bombay phenotype
Answer and explanation in LearnFree account
Question 7 · Hard
A patient with colon cancer and E. coli sepsis types: anti-A 4+, anti-B 1+; A1 cells 0, B cells 4+. The patient's plasma does not react with their own cells. The most likely cause is:
1. AA cold autoantibody
2. BAcquired B antigen
3. CA weak B subgroup
4. DRouleaux formation
Answer and explanation in LearnFree account
Question 8 · Medium
The A and B genes code for:
1. AAntibodies made in the first months of life
2. BMembrane proteins that carry the antigens
3. CTransferases that add a sugar to H antigen
4. DEnzymes that remove fucose from H antigen
Answer and explanation in LearnFree account
Question 9 · Hard
A healthy 28-year-old man of Korean ancestry, a first-time donor, types: anti-A 3+, anti-B 2+, anti-A,B 4+; A1 cells 0, B cells 1+; group O screening cells 0; autocontrol 0. Anti-A1 lectin (Dolichos biflorus) reacts weakly with his cells. He has never been transfused and has had no recent infection. Family studies at the same center show that his mother is group AB, his father is group O and his sister is group O, with all three typings confirmed. Which explanation fits all the findings?
1. AA cis-AB allele inherited from his mother
2. BA2B phenotype with anti-A1 in his plasma
3. CAcquired B antigen on group A red cells
4. DB(A) phenotype from a strong B transferase
Answer and explanation in LearnFree account
Question 10 · Hard
A 41-year-old woman of South Asian ancestry is typed before surgery. Results: anti-A 0, anti-B 0, anti-A,B 0; A1 cells 0, B cells 4+. Anti-H lectin (Ulex europaeus) does not react with her red cells. Her plasma reacts 1+ with group O screening cells at room temperature and is negative at 37 °C and the antiglobulin phase; the autocontrol is negative. She has never been transfused or pregnant. Saliva inhibition studies show both A and H substances in her saliva. The most likely phenotype is:
1. AAm subgroup in a group A secretor
2. BH-deficient secretor (para-Bombay) with an A gene
3. CBombay (Oh) phenotype with an A gene
4. DGroup O with a cold autoantibody
Answer and explanation in LearnFree account
Question 11 · Medium
A group A patient's serum agglutinates A1 reagent cells but not A2 cells, and the patient's cells do not react with Dolichos biflorus lectin. What is the most likely explanation?
1. AThe patient is group AB
2. BBombay phenotype
3. CAcquired B antigen
4. DAn A2 subgroup with anti-A1
Answer and explanation in LearnFree account
Question 12 · Hard
A patient types as group O on forward and reverse grouping. The serum strongly agglutinates group O screening cells at room temperature and 37 °C, and the patient's cells do not react with anti-H lectin (Ulex europaeus). What is the most likely explanation?
1. AA2 subgroup with anti-A1
2. BA cold autoantibody
3. CBombay (Oh) phenotype
4. DRouleaux formation
Answer and explanation in LearnFree account

Antigens: ABO

Results: anti-A 0, anti-B 0; A1 cells 4+, B cells 4+. Group O screening cells and the autocontrol are both 2+ at room temperature. The best next step is:

Ulex europaeus lectin (anti-H) is tested against red cells of several ABO groups. It reacts most strongly with cells of group:

The sugar that gives the A antigen its specificity is:

A patient with no history of transfusion or transplant shows mixed-field agglutination with anti-A and anti-A,B, and has anti-B in the plasma. The most likely subgroup is:

An 88-year-old patient types: anti-A 4+, anti-B 0; A1 cells 0, B cells 0. The antibody screen is negative. What is the best next step?

In ABO grouping, anti-A,B reagent is mainly useful because it:

A patient with colon cancer and E. coli sepsis types: anti-A 4+, anti-B 1+; A1 cells 0, B cells 4+. The patient's plasma does not react with their own cells. The most likely cause is:

The A and B genes code for:

A group A patient's serum agglutinates A1 reagent cells but not A2 cells, and the patient's cells do not react with Dolichos biflorus lectin. What is the most likely explanation?

A patient types as group O on forward and reverse grouping. The serum strongly agglutinates group O screening cells at room temperature and 37 °C, and the patient's cells do not react with anti-H lectin (Ulex europaeus). What is the most likely explanation?