WBC Practical Examination – Procedure, Normal Values & Journal Format 
Introduction
The White Blood Cell (WBC) count is one of the most commonly performed hematological investigations.
For BHMS students, understanding the principle, procedure, precautions, and normal values is essential for practical exams, viva, and journal writing.
This note explains the Total WBC Count using the hemocytometer method, which is the standard technique used in teaching laboratories.
1. Principle of WBC Count
The principle is based on diluting blood with a WBC diluting fluid that destroys red blood cells and stains white blood cells lightly, making them visible for counting under the microscope.
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Diluting fluid used: Turk’s fluid
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RBCs are hemolyzed
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WBC nuclei take up a light stain → become visible
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Cells are counted in a known volume and multiplied to obtain total WBC count per cubic mm of blood
2. Requirements / Apparatus
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Hemocytometer (Neubauer chamber)
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WBC diluting pipette
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Turk’s diluting fluid
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Lancet
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Alcohol swab
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Glass coverslip
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Microscope
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Cotton and gauze
3. Composition of Turk’s Fluid
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Glacial acetic acid → lyses RBCs
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Gentian violet → lightly stains WBC nuclei
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Distilled water → acts as diluent
Function: Clears RBC background and enhances visibility of WBCs.
4. Procedure for Total WBC Count
Step 1: Blood Collection
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Clean fingertip with alcohol swab
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Prick with sterile lancet
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Wipe away first drop
Step 2: Filling the WBC Pipette
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Draw blood up to 0.5 mark
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Draw diluting fluid up to 11 mark
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This produces a 1:20 dilution
Step 3: Mixing
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Roll pipette between palms for uniform mixing
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Discard first few drops (they contain only diluent)
Step 4: Charging the Hemocytometer
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Place coverslip on Neubauer chamber
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Touch pipette tip at the edge of the coverslip
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Allow diluted blood to flow by capillary action
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Avoid overfilling or air bubbles
Step 5: Counting WBCs
Under the microscope:
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Focus on the four large corner squares of the grid
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Count all WBCs present
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Calculate the average
5. Calculation
Formula:
[
\text{Total WBC Count} = \frac{\text{Number of cells counted} \times \text{Dilution factor}}{\text{Volume of area counted}}
]
Values to Remember
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Dilution factor = 20
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Area counted = 4 mm²
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Depth = 0.1 mm
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Volume = 0.4 cu.mm
Example Calculation
If you counted 50 cells in 4 squares:
[
\text{Total WBC Count} = \frac{50 \times 20}{0.4} = 2500 \text{ cells/cu.mm}
]
(This is only an example; actual values vary.)
6. Normal Values of WBC Count
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Adults: 4,000 – 11,000 cells/cu.mm
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Newborns: Higher (10,000 – 25,000 cells/cu.mm)
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Children: 6,000 – 17,000 cells/cu.mm
Values are purely academic for learning purposes.
7. Sources of Error
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Overcharging or undercharging the chamber
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Air bubbles inside chamber
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Dirty coverslip
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Improper mixing of blood and diluent
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Wrong dilution
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Using expired Turk’s fluid
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Counting beyond the correct squares
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Counting artifacts or debris as cells
8. Precautions
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Use clean, dry chamber and coverslip
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Maintain correct dilution
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Mix pipette thoroughly
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Count cells immediately (avoid drying)
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Discard first few drops from pipette
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Do not include cells touching the lower and right borders
9. Viva Questions for BHMS Students
Q1. Why is Turk’s fluid used?
To hemolyze RBCs and lightly stain WBC nuclei.
Q2. How many squares are counted for WBC?
Four large corner squares.
Q3. What is the dilution used?
1:20.
Q4. What is the normal WBC count?
4,000 – 11,000 cells/cu.mm.
Q5. Name two sources of error in WBC count.
Improper dilution, air bubbles.
10. Journal Format (For College Submission)
Title: Total White Blood Cell Count
Aim: To determine the total WBC count using hemocytometer
Principle: Antigen–antibody reaction not involved; RBCs lysed, WBCs stained, counted under microscope
Requirements: Hemocytometer, WBC pipette, Turk’s fluid, microscope
Procedure: (Write the steps)
Calculation: (Include formula and example)
Normal Values: Adults: 4,000–11,000/cu.mm
Precautions: (Write at least 5)
Result: The total WBC count of the given sample is ______ cells/cu.mm
Conclusion
The WBC count is a fundamental hematology practical, and understanding the principle, steps, and sources of error helps BHMS students perform the experiment accurately and confidently in practical exams.
