Diagnostic Laboratory Section

MATERIALS AND METHODS

• The differential count represents the percentage of various leucocytes in stained blood smear .

Materials required

• Clean glass slides
• Leishman’s stain
• Blood cell counter

Procedure

• A thin blood smear is made from pheriperal blood. The smear should not be made up to the edge of the slide. A good smear should be tongue shaped without tails.
• After proper drying of the smear, it is stained with Leishman’s stain and air dried.
• Leishman's staining:

              Prepare and dry the thin blood smear in air.

             Cover the smear with a known quantity of the stain (normally, 8-10   drops) and allow to remain for 1 minute.

            Add double the quantity of neutral distilled water and mix it well with   the stain by means of blowing air through a pipette and allow to   remain for 10-15 minutes.

          Wash off the stain quickly and allow the slide to dry in a vertical position .

• The edge of the smear is examined under oil immersion of the microscope.

• Moving the slide vertically and horizontally, a total of 100 leucocytes are counted using the blood cell counter. Four fields at the edges, centre and tail may be counted.
• The different types of leukocytes are expressed in percentage. The absolute values are calculated for each of the leucocyte after enumerating the total leukocyte count of the sample.

Example

• • Out of 100 leucocytes counted 56 were neutrophils. Total WBC count of the sample is 10,000/cmm.
  • Absolute neutrophil count = 5,600/cmm

Different types of Leukocytes

Neutrophil	Lymphocyte
Eosinophil	Basophil
Monocyte