Determination of the Differential Leukocyte Count (DLC)

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Determination of the Differential Leukocyte Count
(DLC)

• Dr.Sidra Qaiser

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Introduction

• In the differential leucocyte count (DLC) the
  percentage of each type of white blood cells in
  the total leucocyte population is determined.
  Each type of white cells, performs a different
  function in the battle against infections and
  each type of infection yields a different white
  cell picture in the blood. The morphology and
  staining characteristics of each type is peculiar
  and is responsible for the in specific typing.

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Arneth Count

• The age of the neutrophils can be determined by
  the number of lobes of its nucleus. The cells
  having less number of lobes are younger whilst
  with more lobes are relatively older. The maximum
  number of lobes is five in general.

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Requirements

• Clean glass slides, microscope, pricking needle,
  cotton swab, dropper, glass rod, cedar wood oil,
  blow pipe and Leishman's stain comprising of
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• Leishmans powder 0.15 gm
• Methyl alcohol (acetone free) 100 cc
• This stain contains both basophilic and
  eosinophilics (acidophilic) staining components
  and thus helps to discriminate among the granules
  of the differential leucocytes.

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Procedure

• Preparation of blood film
• Sterilize the pricking needle and finger pulp
  with spirit swab and then prick the finger,
  discard the first drop of blood. Now apply the
  slide inverted over the drop of the blood on the
  finger so that some blood sticks to the slide.
  With the help of spreader slide at an angle of
  45 spread the blood drop quickly with a constant
  movement to prepare a thin film. Allow the slide
  to become dry in air. Prepare two or three blood
  film slides.

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Staining of blood film

• Place the slides on the glass rod stand and pour
  20 -30 drops of leishman's stain to cover the
  slide having blood film and allow for 2 minutes.
  Now add distilled water in order to dilute it,
  avoid the spilling over.
• Now wait for 10 minutes. Gently blow through the
  blow pipe for mixing of distilled water and
  Leishman's stain. Extra Leishman's stain is now
  rinsed by pouring the water slowly on the slide
  until the colour becomes pink. Dry the slide in
  the air.

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Counting for DLC

• Choose an area where the film is made quite
  clear. The three parts of a blood film include
  head, body and tail. The body of the film is the
  best area for cell-counting. Place two drops of
  cedar wood oil over the slide The slide is put
  under the oil immersion lens in contact with
  cedar wood oil Now move the slide slowly forward
  and backward from right to left for focusing and
  identification of different types of WBCs Count
  at least 100 cells to determine the percentage of
  DLC.
•  

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Precautions

• The blood film should be thin and smooth.
• The slides used must be clean.
• The staining and blowing should be as gentle as
  possible.
• The lens and slide contact must be carefully
  guarded to avoid the breaking of slides.

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