A tube antiglobulin test reads negative, but IgG-coated control cells added afterwards fail to agglutinate. The most likely cause is:

Unwashed serum globulin neutralised the AHG

The serum was incubated for too long

The test cells carried too much antigen

The patient's antibody was IgM and not IgG

A patient's forward group: anti-A 4+, anti-B 0, anti-A,B 4+. Reverse group: A1 cells 1+, B cells 4+, O cells 0, autocontrol 0. What should be done next to resolve the discrepancy?

Test the red cells with anti-A1 lectin

Perform a direct antiglobulin test

Treat the serum with dithiothreitol

Repeat the forward group on washed cells

Why is a donor whose red cells type D-negative at immediate spin tested further for weak D by the indirect antiglobulin technique?

Weak D cells can immunise a D-negative recipient

Weak D red cells haemolyse quickly in storage

It separates partial D from weak D types

Weak D donors often carry anti-D in their plasma

Blood groups and immunohaematology

35 Kerala MSc MLT Entrance practice questions on Blood groups and immunohaematology, part of Haematology and 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
A tube antiglobulin test reads negative, but IgG-coated control cells added afterwards fail to agglutinate. The most likely cause is:
1. AThe serum was incubated for too long
2. BThe test cells carried too much antigen
3. CUnwashed serum globulin neutralised the AHG
4. DThe patient's antibody was IgM and not IgG
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Answer: C · Unwashed serum globulin neutralised the AHG
Free globulin left by inadequate washing reacts with the anti-human globulin and neutralises it before it can reach coated cells. IgG-sensitised control cells therefore check every negative result: agglutination proves active AHG was present, and failure makes the negative result invalid, so the test must be repeated. Other causes are forgetting to add AHG or using reagent that has lost potency. Cells should be washed at least three times with plenty of saline.
- A: Long incubation can elute weak antibody but does not neutralise the AHG.
- B: The antigen dose on the test cells does not affect the control cells.
- D: An IgM antibody would not stop the control cells reacting with active AHG.
Question 2 · Hard
A patient's forward group: anti-A 4+, anti-B 0, anti-A,B 4+. Reverse group: A1 cells 1+, B cells 4+, O cells 0, autocontrol 0. What should be done next to resolve the discrepancy?
1. ATest the red cells with anti-A1 lectin
2. BPerform a direct antiglobulin test
3. CTreat the serum with dithiothreitol
4. DRepeat the forward group on washed cells
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Answer: A · Test the red cells with anti-A1 lectin
The cells type strongly as group A, but the serum weakly agglutinates A1 cells while O cells and the autocontrol are negative, so the extra reaction is an antibody to A1, not an alloantibody to another antigen or an autoantibody. The usual cause is an A2 or A2B person with anti-A1, found in a small proportion of A2 individuals. Dolichos biflorus lectin (anti-A1) that fails to agglutinate the cells confirms A2, and reverse grouping with A2 cells is negative. The anti-A1 is usually a cold IgM antibody of no clinical significance unless it reacts at 37°C.
- B: A negative autocontrol makes an autoantibody coating the cells unlikely.
- C: DTT disperses IgM, but the antibody's specificity must be found first.
- D: Washing helps with rouleaux or Wharton's jelly, but the forward group here is clear.
Question 3 · Medium
Why is a donor whose red cells type D-negative at immediate spin tested further for weak D by the indirect antiglobulin technique?
1. AWeak D red cells haemolyse quickly in storage
2. BWeak D cells can immunise a D-negative recipient
3. CIt separates partial D from weak D types
4. DWeak D donors often carry anti-D in their plasma
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Answer: B · Weak D cells can immunise a D-negative recipient
Weak D red cells carry fewer D sites, so IgG anti-D may coat them without direct agglutination, and the antiglobulin phase reveals the reaction. Such cells can still immunise, so a weak D positive donor unit is labelled D positive and is not given to D-negative women of childbearing age. Patients, in contrast, are often managed as D negative when their D typing is weak, to avoid anti-D formation in a partial D. Serology cannot separate weak D from partial D; molecular RHD typing is needed for that.
- A: Weak D cells store normally; the concern is immunisation of the recipient.
- C: Weak D and partial D cannot be told apart by the antiglobulin test.
- D: Weak D people do not make anti-D against their own antigen.
Question 4 · Easy
The plasma of a person with the Bombay (Oh) phenotype contains:
1. ANo ABO-related antibodies
2. BAnti-H only
3. CAnti-A and anti-B only
4. DAnti-A, anti-B and anti-H
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Answer: D · Anti-A, anti-B and anti-H
Bombay individuals are homozygous for the silent h allele of FUT1 (hh) and are non-secretors, so they make no H substance and therefore no A or B antigen either. Their red cells type as group O, but their plasma contains potent anti-A, anti-B and anti-H that react at 37°C and can cause severe haemolysis. They can receive blood only from other Bombay donors; the phenotype was first described in Mumbai in 1952. Their red cells do not react with anti-H lectin (Ulex europaeus), unlike group O cells.
- A: Bombay plasma has strong ABO-related antibodies.
- B: Bombay plasma has anti-A and anti-B as well as anti-H.
- C: Ordinary group O plasma has anti-A and anti-B but no anti-H.
Question 5 · Hard
After delivering a D-positive baby, a D-negative mother's acid-elution (Kleihauer) test shows fetal cells at 1.5% of red cells. Take her blood volume as 5,000 mL; one 300 µg anti-D dose covers 30 mL of fetal whole blood; round the doses up and add one. The number of doses needed is:
1. A5 doses
2. B4 doses
3. C6 doses
4. D3 doses
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Answer: B · 4 doses
Fetal bleed = % fetal cells x maternal blood volume / 100 = 1.5 x 5,000 / 100 = 75 mL of fetal whole blood. Doses = 75 / 30 = 2.5, rounded up to 3, plus one for the imprecision of the count = 4 doses of 300 µg. The test works because HbF resists acid elution, so fetal cells stay pink while adult cells become ghosts. Forgetting the extra dose gives 3, and dividing by 15 (the fetal red cell volume a dose covers) gives 5 or 6.
- A: 5 doses divides by 15 mL, the red cell volume, instead of 30 mL of whole blood.
- C: 6 doses divides by the red cell volume and then adds one.
- D: 3 doses forgets the extra dose added for counting imprecision.
Question 6 · Medium
An alloantibody that reacts in the antiglobulin phase stops reacting when the panel cells are pretreated with ficin. Of these, the antibody is most likely:
1. AAnti-Jkb
2. BAnti-Lea
3. CAnti-E
4. DAnti-Fya
Answer and explanation in LearnFree account
Question 7 · Easy
What does the major crossmatch test?
1. ADonor's plasma against patient red cells
2. BPatient's red cells against anti-A and anti-B
3. CPatient's serum against screening cells
4. DPatient's serum against donor red cells
Answer and explanation in LearnFree account
Question 8 · Medium
ABO haemolytic disease of the newborn is usually milder than Rh disease, even though group O mothers have IgG anti-A,B. Why?
1. AMaternal IgG anti-A,B cannot cross the placenta
2. BFetal A and B antigens are weak and widespread in tissues
3. CThe placenta inactivates maternal anti-A and anti-B
4. DABO disease occurs only in the first pregnancy
Answer and explanation in LearnFree account
Question 9 · Easy
The seed lectin of Dolichos biflorus, diluted for routine use, is used in the blood bank to:
1. ADistinguish A1 from A2 red cells
2. BConfirm the presence of weak D antigen
3. CIdentify the secretor status of a donor
4. DDetect H antigen on group O cells
Answer and explanation in LearnFree account
Question 10 · Medium
A weak antibody is suspected to be anti-Jka. Which antigen-positive panel cell gives a reliable exclusion if it is negative?
1. AA homozygous Jk(a+b-) cell
2. BA heterozygous Jk(a+b+) cell
3. CAn enzyme-treated Jk(a-b+) cell
4. DA cord blood Jk(a+b+) cell
Answer and explanation in LearnFree account
Question 11 · Hard
A 74-year-old man with chronic lymphocytic leukaemia gives: anti-A 4+, anti-B 0; A1 cells 0, B cells 0. His serum IgG and IgM are both low, and the autocontrol is negative. What should be done to resolve the discrepancy?
1. ARepeat the forward group with enzyme-treated red cells
2. BReport the patient as group AB from his serum results
3. CIncubate the serum test at room temperature for 15-30 minutes
4. DTest his saliva to confirm his secretor status
Answer and explanation in LearnFree account
Question 12 · Hard
A patient's serum reacts only at the antiglobulin phase with this panel (autocontrol 0). Cell 1: E+ K- Fy(a+) Jk(a+b-), 2+. Cell 2: E- K+ Fy(a+) Jk(a-b+), 0. Cell 3: E+ K- Fy(a-) Jk(a-b+), 0. Cell 4: E- K- Fy(a-) Jk(a+b+), 1+. Cell 5: E- K+ Fy(a+) Jk(a+b-), 2+. Cell 6: E- K- Fy(a-) Jk(a-b+), 0. The antibody is most likely:
1. AAnti-K
2. BAnti-E
3. CAnti-Fya
4. DAnti-Jka
Answer and explanation in LearnFree account
Question 13 · Easy
EDTA blood, rather than clotted blood, is preferred for the direct antiglobulin test because EDTA:
1. AStops IgG antibody from eluting off the cells
2. BPrevents complement binding to cells in vitro
3. CKeeps the red cells from forming rouleaux
4. DPreserves the red cells for longer storage
Answer and explanation in LearnFree account
Question 14 · Medium
Low ionic strength saline (LISS) shortens the incubation time of the indirect antiglobulin test because it:
1. ASpeeds up the binding of antibody to antigen
2. BCross-links IgG molecules on adjacent red cells
3. CRemoves water and concentrates the antibody
4. DRemoves sialic acid from the red cell surface
Answer and explanation in LearnFree account
Question 15 · Hard
Rh phenotyping of a blood donor gives D+ C- c+ E+ e+. Which genotype is he most likely to have?
1. ADcE/dce (R2r)
2. BDCe/DcE (R1R2)
3. CDce/dcE (R0r'')
4. DDcE/DcE (R2R2)
Answer and explanation in LearnFree account
Question 16 · Hard
A group O D-negative mother with anti-D (titre 256) delivers a jaundiced baby who is group A D-positive with a positive DAT. An exchange transfusion is planned. Which red cells should be selected?
1. AGroup A D-negative, compatible with the baby's serum
2. BGroup A D-positive, compatible with the baby's serum
3. CGroup O D-positive, compatible with maternal serum
4. DGroup O D-negative, compatible with maternal serum
Answer and explanation in LearnFree account
Question 17 · Medium
Why is anti-A,B (group O serum) included in some forward grouping protocols in addition to anti-A and anti-B?
1. AIt distinguishes A1 cells from A2 cells
2. BIt detects H antigen on Bombay red cells
3. CIt detects weak A subgroups such as Ax
4. DIt identifies secretors among group O donors
Answer and explanation in LearnFree account
Question 18 · Easy
Treating red cells with papain or ficin strengthens the reactions of antibodies of which blood group system?
1. AMNS
2. BRh
3. CXg
4. DDuffy
Answer and explanation in LearnFree account
Question 19 · Hard
A 22-year-old student recovering from atypical pneumonia has Hb 8.2 g/dL, reticulocytes 9% and red cell agglutinates on the blood film. Polyspecific DAT is positive: anti-IgG negative, anti-C3d positive. His serum agglutinates adult O cells strongly at 4°C and cord cells weakly. The antibody is most likely:
1. AAnti-I
2. BAnti-P
3. CAnti-i
4. DAnti-e
Answer and explanation in LearnFree account
Question 20 · Easy
In Fisher-Race notation, the commonest genotype of D-negative people is:
1. ACde/cde
2. Bcde/cde
3. CcdE/cde
4. DCde/cdE
Answer and explanation in LearnFree account
Question 21 · Hard
A 30-year-old woman with three pregnancies and no transfusions has an antibody screen in which every screening and panel cell reacts 2+ at the antiglobulin phase only. The autocontrol and DAT are negative. The most likely cause is:
1. AAn alloantibody to a high-prevalence antigen
2. BRouleaux from raised plasma globulins
3. CA warm autoantibody against her own cells
4. DA mixture of several common alloantibodies
Answer and explanation in LearnFree account
Question 22 · Medium
A group A patient received two units of group O red cells two days ago. His sample now shows small agglutinates among many free red cells with anti-A. The most likely cause is:
1. AAn A2 subgroup of the patient
2. BThe transfused group O cells
3. CAcquired B antigen on his cells
4. DRouleaux from raised plasma proteins
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Question 23 · Hard
A patient's antibody screen and autocontrol are negative. Of four ABO-compatible units crossmatched by the antiglobulin method, three are compatible and one gives 2+. ABO and D types of patient and unit are confirmed. What is the most appropriate next step?
1. AIssue the unit if the clinician signs for urgency
2. BPerform an elution on the patient's own red cells
3. CRepeat the patient's antibody screen with enzyme cells
4. DPerform a DAT on the incompatible donor's red cells
Answer and explanation in LearnFree account
Question 24 · Medium
A group AB patient's serum agglutinates A1, B and O reagent cells and her own cells (autocontrol) at immediate spin; all are negative at 37°C. Which step will best give a valid reverse group?
1. ARetest her serum against ficin-treated cells
2. BRepeat the forward group using anti-A1 lectin
3. CReport her as group O from the serum results
4. DRepeat the reverse group after cold autoadsorption
Answer and explanation in LearnFree account
Question 25 · Medium
After delivering a D-positive baby, a D-negative mother's blood sample shows rosettes of indicator cells around fetal red cells. What should the laboratory do next?
1. AQuantify the bleed by acid elution or flow cytometry
2. BWithhold anti-D since she is already immunised
3. CGive one standard dose and close the work-up
4. DRepeat the rosette test 72 hours after delivery
Answer and explanation in LearnFree account

10 more Blood groups and immunohaematology questions

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Blood groups and immunohaematology

A tube antiglobulin test reads negative, but IgG-coated control cells added afterwards fail to agglutinate. The most likely cause is:

A patient's forward group: anti-A 4+, anti-B 0, anti-A,B 4+. Reverse group: A1 cells 1+, B cells 4+, O cells 0, autocontrol 0. What should be done next to resolve the discrepancy?

Why is a donor whose red cells type D-negative at immediate spin tested further for weak D by the indirect antiglobulin technique?

The plasma of a person with the Bombay (Oh) phenotype contains:

After delivering a D-positive baby, a D-negative mother's acid-elution (Kleihauer) test shows fetal cells at 1.5% of red cells. Take her blood volume as 5,000 mL; one 300 µg anti-D dose covers 30 mL of fetal whole blood; round the doses up and add one. The number of doses needed is:

An alloantibody that reacts in the antiglobulin phase stops reacting when the panel cells are pretreated with ficin. Of these, the antibody is most likely:

What does the major crossmatch test?

ABO haemolytic disease of the newborn is usually milder than Rh disease, even though group O mothers have IgG anti-A,B. Why?

The seed lectin of Dolichos biflorus, diluted for routine use, is used in the blood bank to:

A weak antibody is suspected to be anti-Jka. Which antigen-positive panel cell gives a reliable exclusion if it is negative?

A 74-year-old man with chronic lymphocytic leukaemia gives: anti-A 4+, anti-B 0; A1 cells 0, B cells 0. His serum IgG and IgM are both low, and the autocontrol is negative. What should be done to resolve the discrepancy?

EDTA blood, rather than clotted blood, is preferred for the direct antiglobulin test because EDTA:

Low ionic strength saline (LISS) shortens the incubation time of the indirect antiglobulin test because it:

Rh phenotyping of a blood donor gives D+ C- c+ E+ e+. Which genotype is he most likely to have?

A group O D-negative mother with anti-D (titre 256) delivers a jaundiced baby who is group A D-positive with a positive DAT. An exchange transfusion is planned. Which red cells should be selected?

Why is anti-A,B (group O serum) included in some forward grouping protocols in addition to anti-A and anti-B?

Treating red cells with papain or ficin strengthens the reactions of antibodies of which blood group system?

In Fisher-Race notation, the commonest genotype of D-negative people is:

A 30-year-old woman with three pregnancies and no transfusions has an antibody screen in which every screening and panel cell reacts 2+ at the antiglobulin phase only. The autocontrol and DAT are negative. The most likely cause is:

A group A patient received two units of group O red cells two days ago. His sample now shows small agglutinates among many free red cells with anti-A. The most likely cause is:

A patient's antibody screen and autocontrol are negative. Of four ABO-compatible units crossmatched by the antiglobulin method, three are compatible and one gives 2+. ABO and D types of patient and unit are confirmed. What is the most appropriate next step?

A group AB patient's serum agglutinates A1, B and O reagent cells and her own cells (autocontrol) at immediate spin; all are negative at 37°C. Which step will best give a valid reverse group?

After delivering a D-positive baby, a D-negative mother's blood sample shows rosettes of indicator cells around fetal red cells. What should the laboratory do next?