Diagnostic Laboratory Section

MATERIALS AND METHODS

Materials

• The equpiments required for performing total leukocyte count are as follows: Blood is drawn up to 0.5 mark in the WBC pipette after mixing it thoroughly.
  • Neubaur counting chamber
  • Coverglass for the counting chamber
  • Diluting pipette

WBC Pipette

• Diluting fluid
• Microscope
• Tally counter

Methods

• Blood adhering to the sides of the pipette is wiped off with cotton.
• The dilution fluid is drawn exactly up to 11 mark, avoiding air bubbles.
• The solution is mixed either by hand or using a pipette shaker for 5 minutes, till all the erythrocytes get haemolysed.
• The first few drops of the solution in the pipette are discarded,later the counting chamber of haemocytometer is charged after placing the special cover slip on the haemocytometer.
• Under low power of the microscope, the number of cells in each of the 4 large squares, each containing 16 small squares are counted following the rules and precautions as per RBC count .
• Caution: A variation of more than 5 cells between any of the four big squares indicates uneven distribution of cells and demands fresh dilution.
• The total number of cells in 4 big squares multiplied by 50 gives the total WBC count in thousands/cmm.
  • 0.5 of blood diluted to 10  
  • 1.0 of blood diluted to 20  
  • Hence dilution factor is 20
• Area of one WBC chamber is 1 mm x 1mm x 0.1 mm
• Total number of WBCs/cmm  = [ ( Total nos of cells in all four squares  X  dilution factor) / 4 ] X  10