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White Blood Cell (Leukocyte) Test (D.L.C, T.L.C)

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In this article you will learn about White Blood Cell (Leukocyte) and it's Pathology test's procedures and Normal values.

LEUKOCYTES (WHITE BLOOD CELL)


These cells have an important function in defence and immunity. They detect foreign or abnormal (antigenic) material and destroy it, through a range of defence mechanisms. Leukocytes are the largest blood cells but they account for only about 1% of the blood volume. They contain nuclei and some have granules in their cytoplasm.


There are two main types:


  • Granulocytes - (polymorphonuclear leukocytes) - neutrophils, eosinophils basophils.


  • Agranulocytes - monocytes and lymphocytes.


Rising white cell numbers in the bloodstream usually indicate a physiological problem, e.g. infection, trauma or malignancy.



white-blood-cell-leukocyte-test-dlc-tlc


DIFFERENTIAL LEUKOCYTE COUNT (DLC)


Principle :

The Polychromatic stain solution (Wriglit, Leishman, Giemsa) contains methylene blue and eosin. These basic and acidic dyes induce multiple colours when applied to cells. Methanol acts as fixative and also as a solvent The fixative does not allow any further changes in the cell and makes them adhere to the glass slide. The basic component of white cell (i.e. cytoplasm) is stained by acidic dyes and they are described as acidophilic; the acidic component (i.e. nucleus with nucleic acid) take blue to purple shades by the basic dyes and they are called basophilic. The neutral components of the cells are stained by both the dyes.


Procedure:


1) Making the blood film smears :

  • Take a clean, ary, grease free slide


  • Transfer a small drop of blood near the edge of the slide.


  • Place the spreader side at an angle of 30° and pull back the spreader until it touches the drop of blood. Let the blood run along the edge of the spreader.


  • Push the spreader forward to the end of the slide with a smooth movement.



2) Staining the film smear :

  • Cover the smear with the staining solution by adding 10-15 drops on the smear and wait for exactly 4-5 minutes.


  • Add an equal number of the drops of the buffer solution. Mix adequately by blowing on it through a pipette. Wait for 12-15 minutes


  • Wash the smear by using tap water.


  • Dry the slide in a drying rack.


3) Examination of film smear:


  • First examine the stained smear under the low power. In an ideal smear three zones will appear.


a) Thick area (Head)


b) Body


c) Thin end of the smear. (tail)


  • Choose the portion slightly before the tail - end where the red cells are beginning to overlap.


  • Place a drop of immersion oil of the smear. Switch to the oil immersion objective and increase the light by opening the iris diaphragm.


  • Examine the film by moving from one field to the next systematically and record the type of leukocyte seen in each field.


  • Count at least a total of 100 leukocytes.


NORMAL RANGE :


Neutrophil = 40 - 80%

Lymphocyte = 20 - 40%

Monocyte = 02 - 10%

Eosinophil = 01 - 06%

Basophil = 0 - 01%


white-blood-cell-leukocyte-test-dlc-tlc


MORPHOLOGY OF LEUKOCYTES


There are two types of leukocytes:


1)Granulocytes :


a) Neutrophils (Polymorphs)


b) Eosinophils


c) Basophils


2) Agranulocytes :


a) Monocytes


b) Lymphocyte



NEUTROPHILS


Size = 10-12


Cytoplasm. = Granules present, stain pale pink.


Nucleus = 2-4 lobes or more


EOSINOPHILS


Size = 10-12 um


Cytoplasm = granules are much larger than the neutrophil granules,


Nucleus = Usually bilobed


white-blood-cell-leukocyte-test-dlc-tlc


BASOPHILS


Size = 8-10 um


Cytoplasm = granules deep purple to black & large.


Nucleus = Round to oval, centrally located.


MONOCYTES


Size = 16-18 um


Cytoplasm = pale grayish blue


nucleus = Kidney shaped or Horseshoe shaped.


LARGE LYMPHOCYTE


Size = 12-15um.


Cytoplasm = Clear Black


Nucleus = Dense smudgy chromatin.


SMALL LYMPHOCYTE


Size = 4-7um.


Cytoplasm = Pink colour


Nucleus = Pale blue in colour.


Clinical significance: Variation in infection.



white-blood-cell-leukocyte-test-dlc-tlc


TOTAL LEUKOCYTE COUNT (TLC)


Principle :

The glacial acetic acid lyses the red cells, while the gentian violet stains the leukocyte nucleus. The blood specimen is diluted 1-20 with the diluting fluid (TURK's solution) and the cells are counted under low power of the microscope by using a Neubauer counting chamber.


Procedure :


  • Make one in 20 dilution with Turk's solution in ratio 0.02ml blood & 0.38 ml Turks solution.


  • Technically charge the counting chamber with the diluted blood.


  • Examine under 10X objective and count the WBC in four large comer squares i.e in WBC section.


  • The total WBCs counts are multiplied by 50 to obtain the WBC count per cumm.


Calculation :

Formula given in figure


white-blood-cell-leukocyte-test-dlc-tlc


Normal Range :


Adults = 4,000 - 10,000 per cumm

At Birth = 10,000 - 25,000 per cumm



Clinical significance :


Increase in W.B.C -

  • Leukemia
  • Rheumatic fever
  • Pregnancy
  • Menstruation
  • Erythroblastosis frtalis
  • Infections


Decrease in W.B.C -

  • Typhoid fever
  • Rheumatoid Arthritis


This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2021 Sanju

Comments

Arpita on February 21, 2021:

Nice article about pathology

Vikas on February 21, 2021:

Great post