A 33-year-old man is evaluated after 18 months of infertility. His semen, collected after 3 days of abstinence, has a volume of 3.0 mL, liquefied within 40 minutes and has a pH of 7.6. It is diluted 1:20 in sodium bicarbonate-formalin diluent and loaded into both sides of an improved Neubauer chamber. Sperm are counted in the five small RBC squares (each 0.04 mm²) of the central large square: 13 on one side and 14 on the other. Using the ASCP reference range, what is the sperm concentration, and how is it interpreted?

13.5 × 10^6/mL [13.5 × 10^9/L]; decreased

1.35 × 10^6/mL [1.35 × 10^9/L]; decreased

27 × 10^6/mL [27 × 10^9/L]; normal

40.5 × 10^6/mL [40.5 × 10^9/L]; normal

The figure shows the cells counted in the four corner squares on one side of a hemocytometer during a manual WBC count. What should the technologist do next?

Clean, refill and recount the chamber

Prepare a higher dilution and recount

Report the mean of the four squares

Average the three similar squares

A child with beta-thalassemia major has a manual WBC count. Blood was diluted 1:20 in 3% acetic acid, and the cells counted in the outlined squares are shown. The film has 25 nRBCs per 100 WBCs. The corrected WBC count is:

6.4 × 10^3/µL (6.4 × 10^9/L)

10.0 × 10^3/µL (10.0 × 10^9/L)

8.0 × 10^3/µL (8.0 × 10^9/L)

6.0 × 10^3/µL (6.0 × 10^9/L)

A manual platelet count uses a 1:100 dilution in 1% ammonium oxalate. Platelets are counted in the central large square (1 mm²) on each side of the chamber: 142 and 158. What is the platelet count?

150 × 10^3/µL (150 × 10^9/L)

300 × 10^3/µL (300 × 10^9/L)

1.5 × 10^3/µL (1.5 × 10^9/L)

Cell counts: manual (hemocytometer)

9 ASCP MLS practice questions on Cell counts: manual (hemocytometer), part of Hematology. The first 9 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
A 33-year-old man is evaluated after 18 months of infertility. His semen, collected after 3 days of abstinence, has a volume of 3.0 mL, liquefied within 40 minutes and has a pH of 7.6. It is diluted 1:20 in sodium bicarbonate-formalin diluent and loaded into both sides of an improved Neubauer chamber. Sperm are counted in the five small RBC squares (each 0.04 mm²) of the central large square: 13 on one side and 14 on the other. Using the ASCP reference range, what is the sperm concentration, and how is it interpreted?
1. A1.35 × 10^6/mL [1.35 × 10^9/L]; decreased
2. B27 × 10^6/mL [27 × 10^9/L]; normal
3. C40.5 × 10^6/mL [40.5 × 10^9/L]; normal
4. D13.5 × 10^6/mL [13.5 × 10^9/L]; decreased
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Answer: D · 13.5 × 10^6/mL [13.5 × 10^9/L]; decreased
Each small RBC square is 0.04 mm², so five squares cover 0.2 mm² and, at a depth of 0.1 mm, hold 0.02 µL. The two sides agree well, so their average of 13.5 sperm is used: 13.5 × 20 ÷ 0.02 µL = 13,500/µL, which is 13.5 × 10^6/mL [13.5 × 10^9/L]. This is below the ASCP reference of more than 20 × 10^6/mL, so the concentration is decreased (oligozoospermia). Adding the two sides without averaging gives 27, leaving out the 0.1 mm depth gives 1.35, and 40.5 × 10^6 is the total count in the 3.0 mL ejaculate, not a concentration. The sodium bicarbonate-formalin diluent immobilizes the sperm so they can be counted.
- A: 1.35 × 10^6/mL leaves out the 0.1 mm chamber depth.
- B: 27 × 10^6/mL comes from adding the two sides instead of averaging them.
- C: 40.5 × 10^6 is the total sperm count per ejaculate, not the concentration.
Question 2 · Medium
The figure shows the cells counted in the four corner squares on one side of a hemocytometer during a manual WBC count. What should the technologist do next?
Figure: MedExams
1. AClean, refill and recount the chamber
2. BPrepare a higher dilution and recount
3. CReport the mean of the four squares
4. DAverage the three similar squares
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Answer: A · Clean, refill and recount the chamber
The bottom-left square holds 78 cells, more than twice the 29-34 cells in each of the other squares. Counts this far apart mean the cells were not spread evenly, usually from poor mixing of the dilution or from overfilling, underfilling or air bubbles in the chamber. Such a count is not valid however it is averaged, so the chamber is cleaned, the dilution is mixed again, and the chamber is recharged and recounted. The counts on the two sides of the chamber should also agree before a result is calculated.
- B: The counts are not too high to count, so a higher dilution does not fix the problem.
- C: Averaging hides the uneven distribution; the count is still unreliable.
- D: Discarding a square selectively biases the count.
Question 3 · Hard
A child with beta-thalassemia major has a manual WBC count. Blood was diluted 1:20 in 3% acetic acid, and the cells counted in the outlined squares are shown. The film has 25 nRBCs per 100 WBCs. The corrected WBC count is:
Figure: MedExams
1. A6.4 × 10^3/µL (6.4 × 10^9/L)
2. B10.0 × 10^3/µL (10.0 × 10^9/L)
3. C8.0 × 10^3/µL (8.0 × 10^9/L)
4. D6.0 × 10^3/µL (6.0 × 10^9/L)
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Answer: A · 6.4 × 10^3/µL (6.4 × 10^9/L)
The four corner squares hold 38 + 42 + 35 + 45 = 160 cells. Count = cells × dilution ÷ (area × depth) = 160 × 20 ÷ (4 mm² × 0.1 mm) = 8,000/µL. Acetic acid lyses red cells but leaves the nuclei of nRBCs, which are counted as white cells, so the count is corrected: 8,000 × 100 ÷ (100 + 25) = 6,400/µL, or 6.4 × 10^3/µL. Laboratories make this correction when nRBCs are high, typically above 10 per 100 WBCs.
- B: Multiplying by 125/100 inverts the correction.
- C: 8.0 × 10^3/µL is the uncorrected count, which still includes the nRBCs.
- D: Subtracting 25% (8,000 × 0.75) is not the correction formula.
Question 4 · Easy
The figure shows one side of an improved Neubauer chamber, with the squares used for a manual WBC count outlined. The total area counted is:
Figure: MedExams
1. A0.2 mm²
2. B4 mm²
3. C1 mm²
4. D9 mm²
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Answer: B · 4 mm²
The improved Neubauer ruling is a 3 mm × 3 mm grid of nine large squares, each 1 mm × 1 mm. A WBC count uses the four corner large squares, so the area counted is 4 × 1 mm² = 4 mm². With the 0.1 mm chamber depth, that is a volume of 0.4 µL, which goes into the count formula. The five small squares inside the centre square, used for RBC counts, cover only 0.2 mm².
- A: 0.2 mm² is the five small central squares used for RBC counts.
- C: 1 mm² is a single large square, such as the centre square used for platelets.
- D: 9 mm² is the whole ruled area.
Question 5 · Hard
A manual platelet count uses a 1:100 dilution in 1% ammonium oxalate. Platelets are counted in the central large square (1 mm²) on each side of the chamber: 142 and 158. What is the platelet count?
1. A300 × 10^3/µL (300 × 10^9/L)
2. B1.5 × 10^3/µL (1.5 × 10^9/L)
3. C15 × 10^3/µL (15 × 10^9/L)
4. D150 × 10^3/µL (150 × 10^9/L)
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Answer: D · 150 × 10^3/µL (150 × 10^9/L)
Average the two sides: (142 + 158) / 2 = 150 platelets per 1 mm². Platelets/µL = 150 × 100 (dilution) / (1 mm² × 0.1 mm depth) = 150,000/µL, or 150 × 10^3/µL (150 × 10^9/L). Ammonium oxalate lyses the red cells so platelets can be seen, usually with phase-contrast microscopy. The two sides should agree closely; if they do not, the chamber is cleaned and refilled.
- A: 300 × 10^3/µL adds both sides but divides by the area of only one.
- B: 1.5 × 10^3/µL leaves out the 1:100 dilution.
- C: 15 × 10^3/µL leaves out the 0.1 mm depth.
Question 6 · Medium
Blood is diluted 1:100 for a hemocytometer WBC count, but the calculation uses a dilution factor of 20. The reported count will be:
1. AFive times the true count
2. BUnchanged from the true count
3. CTwice the true count
4. DOne-fifth of the true count
Answer and explanation in LearnFree account
Question 7 · Easy
What volume of fluid lies over one large (1 mm²) square of an improved Neubauer hemocytometer?
1. A0.004 µL
2. B1.0 µL
3. C0.01 µL
4. D0.1 µL
Answer and explanation in LearnFree account
Question 8 · Hard
Clear, undiluted CSF from a 25-year-old with headache and fever is loaded into a hemocytometer. The technologist counts 36 white cells in all 9 large squares on one side. The WBC count and its interpretation are:
1. A360/µL (360 × 10^6/L), increased
2. B4/µL (4 × 10^6/L), normal
3. C40/µL (40 × 10^6/L), increased
4. D36/µL (36 × 10^6/L), increased
Answer and explanation in LearnFree account
Question 9 · Medium
A white cell count is done in a hemocytometer: 200 cells counted in 4 large squares (total area 4 mm²), dilution 1:20, chamber depth 0.1 mm. What is the WBC count?
1. A100 × 10^9/L
2. B10.0 × 10^9/L
3. C4.0 × 10^9/L
4. D1.0 × 10^9/L
Answer and explanation in LearnFree account

Cell counts: manual (hemocytometer)

The figure shows the cells counted in the four corner squares on one side of a hemocytometer during a manual WBC count. What should the technologist do next?

A child with beta-thalassemia major has a manual WBC count. Blood was diluted 1:20 in 3% acetic acid, and the cells counted in the outlined squares are shown. The film has 25 nRBCs per 100 WBCs. The corrected WBC count is:

The figure shows one side of an improved Neubauer chamber, with the squares used for a manual WBC count outlined. The total area counted is:

A manual platelet count uses a 1:100 dilution in 1% ammonium oxalate. Platelets are counted in the central large square (1 mm²) on each side of the chamber: 142 and 158. What is the platelet count?

Blood is diluted 1:100 for a hemocytometer WBC count, but the calculation uses a dilution factor of 20. The reported count will be:

What volume of fluid lies over one large (1 mm²) square of an improved Neubauer hemocytometer?

Clear, undiluted CSF from a 25-year-old with headache and fever is loaded into a hemocytometer. The technologist counts 36 white cells in all 9 large squares on one side. The WBC count and its interpretation are:

A white cell count is done in a hemocytometer: 200 cells counted in 4 large squares (total area 4 mm²), dilution 1:20, chamber depth 0.1 mm. What is the WBC count?