The formula for calculating a white blood cell (WBC) count depends on the method used. Here are some common formulas:
- Manual Count using a Hemocytometer:
- WBC (cells/mm3) = Cells counted x 20 (=dilution factor) / Volume (=0.4 mm) = Number of cells counted x 50
- This formula is used when counting WBCs manually using a hemocytometer.
- Automated Cell Counter: Automated cell counters use various methods to count WBCs, and the specific formula depends on the instrument and method used.
- Absolute Cell Count Calculation:
- Absolute (Abs) lymphs = WBC count x 1000 x percent lymphs (expressed as a decimal)
- This formula can be used to calculate absolute cell counts for different types of white blood cells.
Examples:
- If you count 50 WBCs in a hemocytometer using a dilution factor of 20 and a volume of 0.4 mm, then the WBC count would be: 50 x 20 / 0.4 = 2500 cells/mm3.
- If a patient's WBC count is 8,000 cells/mm3 and their lymphocyte percentage is 35%, then their absolute lymphocyte count would be: 8000 x 1000 x 0.35 = 2,800,000 cells/mm3.
Practical Insights:
- WBC count is a common laboratory test used to diagnose various conditions, including infections, inflammation, and certain types of cancer.
- The reference range for a normal WBC count varies depending on age, gender, and other factors.
- A WBC count can be elevated (leukocytosis) or decreased (leukopenia) depending on the underlying medical condition.
