Blood collection, cell counts and red cell indices

70 Lab technician recruitment practice questions on Blood collection, cell counts and red cell indices, part of Haematology. 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
In an impedance cell counter, the size of each cell is measured by:
1. ANumber of pulses per second
2. BColour of the cell
3. CHeight of the voltage pulse
4. DAngle of scattered light
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Answer: C · Height of the voltage pulse
In the Coulter principle, a cell passing through the aperture displaces conducting fluid and raises resistance. The number of pulses gives the count and pulse height is proportional to cell volume.
- A: Pulse number gives the count, not the size.
- B: Impedance does not detect colour.
- D: Light scatter is used in optical counters.
Question 2 · Hard
A Westergren tube shows a hazy, sloping boundary between plasma and red cells after one hour. The likely cause is:
1. ACorrect citrate ratio
2. BExactly vertical tube
3. CMany reticulocytes
4. DSample tested too quickly
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Answer: C · Many reticulocytes
Reticulocytes are lighter and settle more slowly, giving a hazy layer known as stratified sedimentation. The reading is taken at the top of the main red cell column.
- A: A correct ratio does not cause haziness.
- B: A vertical tube is correct.
- D: Prompt testing is correct practice.
Question 3 · Medium
When only a citrate tube is drawn with a winged butterfly set, why is a discard tube filled first?
1. ATo flush out heparin
2. BTo remove clotted blood
3. CTo clear air from the tubing
4. DTo warm the needle
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Answer: C · To clear air from the tubing
The tubing of a butterfly set holds air, which would underfill the first tube and upset the 9 : 1 ratio. A plain discard tube fills the dead space. The full order of draw is culture, citrate, serum, heparin, EDTA, fluoride.
- A: A new butterfly set carries no heparin.
- B: Fresh venepuncture blood has no clot to remove.
- D: Warming plays no part.
Question 4 · Hard
A Westergren ESR is set up with 1.6 mL blood and 0.4 mL citrate, and the room is at 35 °C. What effect does the room temperature have?
1. AFalsely low ESR
2. BNo effect at all
3. CFalsely high ESR
4. DHaemolysis of the sample
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Answer: C · Falsely high ESR
The 4 : 1 ratio is correct, but heat lowers plasma viscosity and speeds sedimentation. ICSH asks for 18-25 °C, away from sunlight and vibration.
- A: Low temperature, not high, slows the ESR.
- B: Temperature does affect sedimentation.
- D: Mild heat does not lyse cells.
Question 5 · Easy
How deep may an infant heel puncture go, at most?
1. A2.0 mm
2. B4.0 mm
3. C5.0 mm
4. D0.5 mm
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Answer: A · 2.0 mm
CLSI limits infant heel puncture to 2.0 mm to avoid the calcaneus. The side of the plantar heel is used.
- B: 4.0 mm is too deep.
- C: 5.0 mm risks bone injury.
- D: 0.5 mm gives too little blood flow.
Question 6 · Medium
Which factor increases the ESR?
1. ARaised fibrinogen
2. BSickle cells
3. CSpherocytosis
4. DPolycythaemia
Answer and explanation in LearnFree account
Question 7 · Medium
Which feature of the Fuchs-Rosenthal chamber makes it suitable for CSF cell counts?
1. AShallower depth
2. BBuilt-in staining
3. CLarger volume counted
4. DNo ruling at all
Answer and explanation in LearnFree account
Question 8 · Medium
Which error falsely raises the analyser WBC count?
1. ALow haemoglobin
2. BNucleated red cells
3. CHaemolysis of the sample
4. DPlatelet clumping only in citrate
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Question 9 · Easy
What is the usual dilution of blood for a manual red cell count with an RBC pipette?
1. A1 in 100
2. B1 in 2000
3. C1 in 20
4. D1 in 200
Answer and explanation in LearnFree account
Question 10 · Medium
Why should a capillary sample not be taken by squeezing the finger hard?
1. ATissue fluid dilutes the blood
2. BPlatelet count rises
3. CThe blood clots instantly
4. DRed cells are lysed by pressure
Answer and explanation in LearnFree account
Question 11 · Medium
A patient with Hb 9 g/dL has MCV 68 fL, MCH 20 pg and raised RDW. This pattern most suggests:
1. AAcute blood loss
2. BVitamin B12 deficiency
3. CIron deficiency anaemia
4. DBeta thalassaemia trait
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Question 12 · Medium
During automated counting, a histogram shows an RBC peak with a shoulder on the right. This suggests:
1. ALipaemia
2. BLow haemoglobin only
3. CA second population of larger cells
4. DPlatelet clumping
Answer and explanation in LearnFree account
Question 13 · Medium
Which correction to ESR is needed in a severely anaemic patient?
1. ANone is routinely applied
2. BReport only Wintrobe
3. CSubtract PCV from ESR
4. DMultiply the ESR by two
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Question 14 · Hard
After spinning a Wintrobe tube, the total column is 80 mm and the red cell column 36 mm. The PCV is:
1. A55%
2. B45%
3. C44%
4. D36%
Answer and explanation in LearnFree account
Question 15 · Easy
Which of these is NOT a sign of haemolysis in a sample?
1. AFalsely raised potassium
2. BStraw-coloured clear plasma
3. CPink or red plasma
4. DRaised LDH
Answer and explanation in LearnFree account
Question 16 · Easy
MCH is expressed in:
1. APercentage
2. BPicograms
3. CGrams per decilitre
4. DFemtolitres
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Question 17 · Hard
A WBC count is done with a 1 in 20 dilution, but cells are counted in only one corner square, giving 45 cells. The WBC per µL is:
1. A9000
2. B2250
3. C4500
4. D900
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Question 18 · Easy
In the Westergren method, the ESR tube is held:
1. AExactly vertical
2. BHorizontal
3. CAt 45 degrees
4. DSlightly tilted
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Question 19 · Easy
Which anticoagulant is used for the Westergren ESR as recommended by ICSH?
1. ASodium fluoride
2. BSodium citrate or diluted EDTA
3. CLithium heparin alone
4. DUndiluted dry oxalate
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Question 20 · Hard
A manual platelet count with 1 in 20 dilution in ammonium oxalate gives 150 platelets in the central large square. The platelet count per µL is:
1. A30 000
2. B7500
3. C150 000
4. D300 000
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Question 21 · Medium
Why must EDTA blood be mixed by gentle inversion right after collection?
1. ATo warm the sample
2. BTo raise the platelet count
3. CTo lyse the red cells
4. DTo prevent micro-clots
Answer and explanation in LearnFree account
Question 22 · Hard
A Sahli reading of 9 g/dL is reported, but HiCN on the same blood gives 11 g/dL. Which pipette fault fits best?
1. AToo much acid was used
2. BThe pipette was overfilled
3. CThe tube was read too late
4. DThe pipette was not rinsed out
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Question 23 · Hard
A sample has RBC 5.5 million/µL, Hb 11 g/dL and PCV 35%. Which index pattern results?
1. AMCV 64 fL, MCH 20 pg
2. BMCV 90 fL, MCH 30 pg
3. CMCV 110 fL, MCH 35 pg
4. DMCV 64 fL, MCH 31 pg
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Question 24 · Easy
EDTA plasma is unsuitable for which test?
1. AHbA1c
2. BSerum calcium
3. CBlood count
4. DBlood grouping
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Question 25 · Medium
On a manual WBC count of a newborn, many nucleated red cells are present. What correction is needed?
1. ANo correction is needed
2. BRepeat with Hayem's fluid
3. CMultiply the count by two
4. DApply nRBC correction
Answer and explanation in LearnFree account

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Blood collection, cell counts and red cell indices

In an impedance cell counter, the size of each cell is measured by:

A Westergren tube shows a hazy, sloping boundary between plasma and red cells after one hour. The likely cause is:

When only a citrate tube is drawn with a winged butterfly set, why is a discard tube filled first?

A Westergren ESR is set up with 1.6 mL blood and 0.4 mL citrate, and the room is at 35 °C. What effect does the room temperature have?

How deep may an infant heel puncture go, at most?

Which factor increases the ESR?

Which feature of the Fuchs-Rosenthal chamber makes it suitable for CSF cell counts?

Which error falsely raises the analyser WBC count?

What is the usual dilution of blood for a manual red cell count with an RBC pipette?

Why should a capillary sample not be taken by squeezing the finger hard?

A patient with Hb 9 g/dL has MCV 68 fL, MCH 20 pg and raised RDW. This pattern most suggests:

During automated counting, a histogram shows an RBC peak with a shoulder on the right. This suggests:

Which correction to ESR is needed in a severely anaemic patient?

After spinning a Wintrobe tube, the total column is 80 mm and the red cell column 36 mm. The PCV is:

Which of these is NOT a sign of haemolysis in a sample?

MCH is expressed in:

A WBC count is done with a 1 in 20 dilution, but cells are counted in only one corner square, giving 45 cells. The WBC per µL is:

In the Westergren method, the ESR tube is held:

Which anticoagulant is used for the Westergren ESR as recommended by ICSH?

A manual platelet count with 1 in 20 dilution in ammonium oxalate gives 150 platelets in the central large square. The platelet count per µL is:

Why must EDTA blood be mixed by gentle inversion right after collection?

A Sahli reading of 9 g/dL is reported, but HiCN on the same blood gives 11 g/dL. Which pipette fault fits best?

A sample has RBC 5.5 million/µL, Hb 11 g/dL and PCV 35%. Which index pattern results?

EDTA plasma is unsuitable for which test?

On a manual WBC count of a newborn, many nucleated red cells are present. What correction is needed?