Anti-Jka in a patient's serum hemolyzes Jk(a+) panel cells, but the same antibody tested in EDTA plasma causes no hemolysis. Why?

EDTA binds the calcium that complement needs

Plasma contains less antibody than serum

EDTA destroys Kidd antigens on the cells

EDTA stops the antibody binding to the cells

A patient with multiple myeloma has 2+ reactions with every panel cell and the autocontrol at immediate spin, and none at the antiglobulin phase. Under the microscope the cells lie in stacks like coins, and the reactions disperse when saline replaces the plasma. The cause is:

Rouleaux from the high plasma protein

A warm autoantibody coating the cells

A cold autoantibody such as anti-I

An alloantibody to a high-prevalence antigen

Anti-Fya is the only specificity not excluded. Two Fy(a+) panel cells react and five Fy(a-) cells do not. Before anti-Fya is reported by the rule of three, the laboratory should:

Test at least one more Fy(a+) cell

Test at least one more Fy(a-) cell

Report anti-Fya, as the rule is already met

Repeat the same panel with a new sample

Antibody screening and identification

28 DOH Abu Dhabi (HAAD) lab licensing practice questions on Antibody screening and identification, part of Blood Banking. The first 25 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 · Medium
Panel reactions occur at immediate spin only (37 °C and antiglobulin phases negative, autocontrol negative): cell 1 M+N- P1+ Le(a-) 2+; cell 2 M+N+ P1- Le(a+) 1+; cell 3 M-N+ P1+ Le(a-) 0; cell 4 M+N- P1- Le(a-) 2+; cell 5 M-N+ P1+ Le(a+) 0. The antibody is most likely:
1. AAnti-P1
2. BAnti-M
3. CAnti-N
4. DAnti-Lea
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Answer: B · Anti-M
Only the M-positive cells react, and the M+N- (homozygous) cells react more strongly than the M+N+ cell, which is dosage. Anti-N is excluded by the nonreactive N-positive cells 3 and 5, anti-P1 by the nonreactive P1-positive cells 3 and 5, and anti-Lea by cell 5. Anti-M reacting only at room temperature is usually not clinically significant, so units compatible at 37 °C and the antiglobulin phase are normally suitable. Anti-M that reacts at 37 °C should be treated as potentially significant.
- A: Anti-P1 is excluded because the P1-positive cells 3 and 5 do not react.
- C: Anti-N is excluded because the N-positive cells 3 and 5 do not react.
- D: Anti-Lea is excluded because the Le(a+) cell 5 does not react.
Question 2 · Medium
Anti-Jka in a patient's serum hemolyzes Jk(a+) panel cells, but the same antibody tested in EDTA plasma causes no hemolysis. Why?
1. APlasma contains less antibody than serum
2. BEDTA destroys Kidd antigens on the cells
3. CEDTA stops the antibody binding to the cells
4. DEDTA binds the calcium that complement needs
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Answer: D · EDTA binds the calcium that complement needs
Complement activation needs calcium and magnesium ions, and EDTA chelates both. In EDTA plasma the antibody can still bind and coat the cells, but complement cannot complete the lytic pathway, so no hemolysis is seen. With serum, hemolysis must be read as a positive reaction, as it is for anti-Jka, anti-Lea and anti-Vel. Laboratories using EDTA plasma rely on the antiglobulin reading to detect these antibodies.
- A: Serum and plasma contain the same amount of antibody.
- B: EDTA does not damage Kidd antigens.
- C: EDTA does not stop binding; the coated cells still react at the antiglobulin phase.
Question 3 · Medium
A patient with multiple myeloma has 2+ reactions with every panel cell and the autocontrol at immediate spin, and none at the antiglobulin phase. Under the microscope the cells lie in stacks like coins, and the reactions disperse when saline replaces the plasma. The cause is:
1. AA warm autoantibody coating the cells
2. BA cold autoantibody such as anti-I
3. CAn alloantibody to a high-prevalence antigen
4. DRouleaux from the high plasma protein
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Answer: D · Rouleaux from the high plasma protein
High concentrations of abnormal protein, as in myeloma, make red cells stick together face to face. Rouleaux looks like agglutination in unwashed tests but disperses when the plasma is replaced with saline, while true agglutinates remain. It disappears at the antiglobulin phase because washing removes the plasma. The saline replacement technique also helps resolve reverse ABO grouping problems in these patients.
- A: A warm autoantibody reacts at the antiglobulin phase, which is negative here.
- B: Agglutination by a cold autoantibody does not disperse when the plasma is replaced with saline.
- C: A high-prevalence alloantibody would react at the antiglobulin phase and not with the autocontrol.
Question 4 · Hard
Panel results, autocontrol negative at all phases (IS = immediate spin, AHG = antiglobulin phase): cell 1 P1+ M+N+ K- Fy(a+b-): IS 2+, AHG 2+; cell 2 P1+ M-N+ K+ Fy(a-b+): IS 2+, AHG 0; cell 3 P1- M+N- K- Fy(a+b+): IS 0, AHG 1+; cell 4 P1- M+N- K- Fy(a-b+): IS 0, AHG 0; cell 5 P1+ M-N+ K+ Fy(a+b-): IS 1+, AHG 2+; cell 6 P1- M-N+ K- Fy(a-b+): IS 0, AHG 0. Which antibodies are present?
1. AAnti-P1 and anti-Fya
2. BAnti-Fya alone
3. CAnti-M and anti-Fya
4. DAnti-P1 and anti-K
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Answer: A · Anti-P1 and anti-Fya
The immediate-spin reactions follow P1: the three P1-positive cells react and the P1-negative cells do not, the pattern of a cold IgM antibody. The antiglobulin reactions follow Fya, with stronger reactions on the Fy(a+b-) cells than on the Fy(a+b+) cell. Anti-M is excluded by the nonreactive M+N- cells 3 and 4 at immediate spin, and anti-K by the nonreactive K-positive cell 2 at the antiglobulin phase. Anti-Fya is clinically significant, so Fy(a-) units compatible by AHG crossmatch are needed, while anti-P1 reacting only at room temperature usually needs no special selection.
- B: Anti-Fya alone does not explain the immediate-spin reaction of the Fy(a-) cell 2.
- C: Anti-M is excluded because the M+N- cells 3 and 4 do not react at immediate spin.
- D: Anti-K is excluded because the K-positive cell 2 does not react at the antiglobulin phase.
Question 5 · Medium
Anti-Fya is the only specificity not excluded. Two Fy(a+) panel cells react and five Fy(a-) cells do not. Before anti-Fya is reported by the rule of three, the laboratory should:
1. ATest at least one more Fy(a-) cell
2. BReport anti-Fya, as the rule is already met
3. CTest at least one more Fy(a+) cell
4. DRepeat the same panel with a new sample
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Answer: C · Test at least one more Fy(a+) cell
The rule of three asks for at least three antigen-positive cells that react and three antigen-negative cells that do not, which gives a probability of about 0.05 or less that the pattern is due to chance. Here the negative side is met with five Fy(a-) cells, but only two Fy(a+) cells react. Testing one or more extra Fy(a+) cells, ideally Fy(a+b-), completes the evidence. Typing the patient's red cells as Fy(a-) further supports the identification.
- A: Five antigen-negative cells already meet the negative side of the rule.
- B: Only two antigen-positive cells react, so the rule is not yet met.
- D: Repeating the same cells adds no new antigen-positive results.
Question 6 · Medium
Anti-Fya and anti-Jkb are both still possible, because every reactive panel cell is Fy(a+) and Jk(b+). Which additional cells will best separate them?
1. AMore cells that are Fy(a+) and Jk(b+)
2. BFy(a+) Jk(b-) cells and Fy(a-) Jk(b+) cells
3. CThe patient's own cells as an autocontrol
4. DMore cells that are Fy(a-) and Jk(b-)
Answer and explanation in LearnFree account
Question 7 · Hard
Antiglobulin-phase panel, autocontrol negative: cell 1 R1R1, K-, Fy(a+b-), Jk(a+b-): 0; cell 2 R2R2, K-, Fy(a-b+), Jk(a-b+): 2+; cell 3 rr, K+, Fy(a+b+), Jk(a+b+): 0; cell 4 R1r, K-, Fy(a-b+), Jk(a+b-): 0; cell 5 rr, K-, Fy(a+b-), Jk(a-b+): 0; cell 6 R2r, K-, Fy(a+b+), Jk(a+b+): 2+. The most likely specificity is:
1. AAnti-c
2. BAnti-Fyb
3. CAnti-E
4. DAnti-Jkb
Answer and explanation in LearnFree account
Question 8 · Hard
After a panel, anti-c, anti-Fya and anti-Jkb cannot be excluded. The patient, not transfused for a year, types c+, Fy(a-b+) and Jk(a+b-). Which antibodies remain possible?
1. AAnti-c and anti-Fya
2. BAnti-Fya and anti-Jkb
3. CAnti-c, anti-Fya and anti-Jkb
4. DAnti-c and anti-Jkb
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Question 9 · Easy
In an antibody identification panel, the autocontrol tube contains:
1. AThe patient's own plasma and red cells
2. BSaline and the patient's own red cells
3. CThe patient's plasma and pooled group O cells
4. DThe patient's red cells and anti-IgG reagent only
Answer and explanation in LearnFree account
Question 10 · Hard
A man with myelodysplasia, transfused every 3 weeks, has known anti-K. His new sample is tested against K- panel cells at the antiglobulin phase: cell 1 Jk(a+b-) Fy(a+b-) S+s- 2+; cell 2 Jk(a+b+) Fy(a-b+) S-s+ 1+; cell 3 Jk(a-b+) Fy(a-b+) S-s+ 0; cell 4 Jk(a+b-) Fy(a-b+) S-s+ 2+; cell 5 Jk(a-b+) Fy(a+b-) S+s- 0. What new antibody is present?
1. AAnti-Jkb
2. BAnti-Fyb
3. CAnti-Jka
4. DAnti-s
Answer and explanation in LearnFree account
Question 11 · Medium
Screening cell II gives a 1+ result with anti-IgG; screening cells I and III and an 11-cell panel give none, and so does the autocontrol. What does this pattern most likely show?
1. AAnti-A or anti-B reacting with cell II
2. BAn antibody to a low-prevalence antigen on cell II
3. CAn antibody to a high-prevalence antigen
4. DAn autoantibody to the patient's own cells
Answer and explanation in LearnFree account
Question 12 · Hard
Antiglobulin-phase panel, autocontrol negative: cell 1 R1R1, K+, Fy(a+b-), Jk(a+b+): 2+; cell 2 R2R2, K-, Fy(a+b+), Jk(a-b+): 2+; cell 3 rr, K-, Fy(a-b+), Jk(a+b-): 0; cell 4 R1R1, K-, Fy(a+b-), Jk(a-b+): 0; cell 5 R2r, K+, Fy(a-b+), Jk(a+b-): 3+; cell 6 rr, K-, Fy(a+b-), Jk(a+b+): 0. Which antibodies best explain these results?
1. AAnti-E and anti-Fya
2. BAnti-E and anti-K
3. CAnti-E alone
4. DAnti-C and anti-K
Answer and explanation in LearnFree account
Question 13 · Hard
A 72-year-old man's panel shows 3+ reactions with every cell and the autocontrol at immediate spin, none at 37 °C, and 1+ reactions with polyspecific AHG. His DAT is positive with anti-C3d only. Which change best reveals any clinically significant alloantibodies?
1. AUse anti-IgG AHG and skip the immediate-spin reading
2. BMake an eluate from his red cells and test it
3. CUse ficin-treated panel cells with polyspecific AHG
4. DIncubate and read all tubes at room temperature
Answer and explanation in LearnFree account
Question 14 · Easy
Antibody screening cells are always group O. The reason is that group O cells:
1. ALack every clinically significant antigen
2. BCarry stronger Rh antigens than other groups
3. CWill not react with the patient's anti-A or anti-B
4. DAre less easily lysed by complement
Answer and explanation in LearnFree account
Question 15 · Hard
A woman with myeloma started daratumumab (anti-CD38) last month. Her antibody screen now reacts with every cell at the antiglobulin phase, but a screen with DTT-treated cells is negative. She types K-negative. Which red cells should be issued?
1. ANo units until the drug has cleared
2. BAny units of her ABO and D group
3. CGroup O, D-negative units only
4. DK-negative units of her ABO and D group
Answer and explanation in LearnFree account
Question 16 · Medium
A 58-year-old man, not transfused for at least a year, has 2+ reactions with every panel cell and with the autocontrol at the antiglobulin phase. His DAT is positive with anti-IgG. What is the most likely cause?
1. AA delayed hemolytic transfusion reaction
2. BA warm autoantibody
3. CAn alloantibody to a high-prevalence antigen
4. DA cold autoantibody such as anti-I
Answer and explanation in LearnFree account
Question 17 · Hard
Only three panel cells are nonreactive at the antiglobulin phase: R1R1, K-, Fy(a+b-), Jk(a+b-), M+N-, S+s+; rr, K+, Fy(a-b+), Jk(a-b+), M-N+, S-s+; and R2R2, K-, Fy(a+b+), Jk(a+b+), M+N+, S+s+. The laboratory excludes Rh, Duffy, Kidd and MNS antigens only with homozygous cells. Which antibody cannot yet be excluded?
1. AAnti-S
2. BAnti-N
3. CAnti-s
4. DAnti-Jkb
Answer and explanation in LearnFree account
Question 18 · Hard
In a PEG antiglobulin panel, every cell and the autocontrol react 1+. The DAT on a fresh EDTA sample is negative, and the patient has never been transfused. What is the most likely explanation?
1. AA warm autoantibody coating the cells in the body
2. BAlloantibody bound to recently transfused cells
3. CReactivity that depends on the PEG medium
4. DAn alloantibody to a high-prevalence antigen
Answer and explanation in LearnFree account
Question 19 · Medium
A 50-year-old man, last transfused 2 years ago, has a positive antibody screen. Every panel cell reacts 2+ at the antiglobulin phase only; the autocontrol and DAT are negative, and he takes no regular medicines. The most likely cause is:
1. ARouleaux from raised plasma proteins
2. BAn alloantibody to a high-prevalence antigen
3. CA warm autoantibody
4. DA cold autoantibody such as anti-I
Answer and explanation in LearnFree account
Question 20 · Medium
In the prewarm technique, the patient's plasma and the red cells are warmed to 37 °C separately before they are mixed. The purpose is to:
1. AInactivate complement in the plasma
2. BRemove IgG antibodies from the plasma
3. CMake IgM antibodies bind more strongly to cells
4. DStop cold-reacting antibodies from binding
Answer and explanation in LearnFree account
Question 21 · Hard
A 52-year-old man, never transfused, needs 2 units for a knee replacement; hemoglobin 128 g/L (12.8 g/dL). He types group A, D-positive, and his cells react with Dolichos biflorus lectin; reverse grouping: A1 cells 0, B cells 4+. LISS tube antibody screen: all three group O cells give 2+ at immediate spin, 1+ when read after 37 °C incubation, and 0 at the antiglobulin phase with anti-IgG. The autocontrol is 0 at every phase. Group A2 reagent cells give 2+ at immediate spin, and group A1 cells give 0. Which red cells are most suitable?
1. ABombay (Oh) units from a rare registry
2. BGroup O units, as universal red cells
3. CGroup A units, crossmatch-compatible
4. DGroup A2 units, which lack A1
Answer and explanation in LearnFree account
Question 22 · Hard
A 62-year-old man, last transfused 5 months ago, has a positive antibody screen before hip surgery. Antiglobulin-phase panel, untreated cells then ficin-treated cells, autocontrol negative throughout: cell 1 R1R1, K-, Fy(a+b-), Jk(a-b+): 2+, 0; cell 2 R2R2, K-, Fy(a-b+), Jk(a-b+): 2+, 3+; cell 3 rr, K+, Fy(a-b+), Jk(a+b+): 0, 0; cell 4 R1r, K-, Fy(a+b+), Jk(a-b+): 1+, 0; cell 5 R2r, K-, Fy(a-b+), Jk(a+b-): 2+, 3+; cell 6 rr, K-, Fy(a-b+), Jk(a+b-): 0, 0. The antibodies present are:
1. AAnti-E and anti-C
2. BAnti-E and anti-Fya
3. CAnti-E and anti-Jkb
4. DAnti-D alone
Answer and explanation in LearnFree account
Question 23 · Hard
A 47-year-old woman with myelodysplasia, four previous pregnancies and many platelet transfusions now shows poor platelet count increments after transfusion. Her antibody screen is weakly positive. An 11-cell antiglobulin-phase panel gives weak to 1+ reactions with cells 2, 5 and 9 only. These three cells share no red cell antigen that the other eight cells lack, and other cells carrying the same Rh, Kell, Duffy, Kidd and MNS antigens are nonreactive. A repeat panel gives the same pattern. The autocontrol and DAT are negative. After chloroquine diphosphate treatment, cells 2, 5 and 9 no longer react. These reactions are best explained by:
1. AA warm autoantibody of low avidity
2. BA weak anti-Jka showing dosage
3. CAnti-Bg (HLA class I) antibodies
4. DAn antibody to a low-prevalence antigen
Answer and explanation in LearnFree account
Question 24 · Medium
A pre-operative antibody screen is positive, and the panel shown is tested. Which antibody is most likely present?
Figure: MedExams
1. AAnti-Lea
2. BAnti-P1
3. CAnti-I
4. DAnti-M
Answer and explanation in LearnFree account
Question 25 · Hard
A 64-year-old woman, transfused 3 weeks ago, has a positive antibody screen before a further transfusion. Her panel is shown. The antibody most likely present is:
Figure: MedExams
1. AAnti-M
2. BAnti-e
3. CAnti-Jka
4. DAnti-N
Answer and explanation in LearnFree account

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Antibody screening and identification

Panel reactions occur at immediate spin only (37 °C and antiglobulin phases negative, autocontrol negative): cell 1 M+N- P1+ Le(a-) 2+; cell 2 M+N+ P1- Le(a+) 1+; cell 3 M-N+ P1+ Le(a-) 0; cell 4 M+N- P1- Le(a-) 2+; cell 5 M-N+ P1+ Le(a+) 0. The antibody is most likely:

Anti-Jka in a patient's serum hemolyzes Jk(a+) panel cells, but the same antibody tested in EDTA plasma causes no hemolysis. Why?

A patient with multiple myeloma has 2+ reactions with every panel cell and the autocontrol at immediate spin, and none at the antiglobulin phase. Under the microscope the cells lie in stacks like coins, and the reactions disperse when saline replaces the plasma. The cause is:

Anti-Fya is the only specificity not excluded. Two Fy(a+) panel cells react and five Fy(a-) cells do not. Before anti-Fya is reported by the rule of three, the laboratory should:

Anti-Fya and anti-Jkb are both still possible, because every reactive panel cell is Fy(a+) and Jk(b+). Which additional cells will best separate them?

After a panel, anti-c, anti-Fya and anti-Jkb cannot be excluded. The patient, not transfused for a year, types c+, Fy(a-b+) and Jk(a+b-). Which antibodies remain possible?

In an antibody identification panel, the autocontrol tube contains:

Screening cell II gives a 1+ result with anti-IgG; screening cells I and III and an 11-cell panel give none, and so does the autocontrol. What does this pattern most likely show?

A 72-year-old man's panel shows 3+ reactions with every cell and the autocontrol at immediate spin, none at 37 °C, and 1+ reactions with polyspecific AHG. His DAT is positive with anti-C3d only. Which change best reveals any clinically significant alloantibodies?

Antibody screening cells are always group O. The reason is that group O cells:

A woman with myeloma started daratumumab (anti-CD38) last month. Her antibody screen now reacts with every cell at the antiglobulin phase, but a screen with DTT-treated cells is negative. She types K-negative. Which red cells should be issued?

A 58-year-old man, not transfused for at least a year, has 2+ reactions with every panel cell and with the autocontrol at the antiglobulin phase. His DAT is positive with anti-IgG. What is the most likely cause?

In a PEG antiglobulin panel, every cell and the autocontrol react 1+. The DAT on a fresh EDTA sample is negative, and the patient has never been transfused. What is the most likely explanation?

A 50-year-old man, last transfused 2 years ago, has a positive antibody screen. Every panel cell reacts 2+ at the antiglobulin phase only; the autocontrol and DAT are negative, and he takes no regular medicines. The most likely cause is:

In the prewarm technique, the patient's plasma and the red cells are warmed to 37 °C separately before they are mixed. The purpose is to:

A pre-operative antibody screen is positive, and the panel shown is tested. Which antibody is most likely present?

A 64-year-old woman, transfused 3 weeks ago, has a positive antibody screen before a further transfusion. Her panel is shown. The antibody most likely present is: