White blood cell:- Part 2 – Total Leukocytes Count Procedure, TLC Solution Preparation

Sample

1. EDTA blood is needed.
2. Oxalate or citrated blood can also be used.

Purpose of the test (Indications)

1. To differentiate between acute and chronic infection.
2. To follow the patient with chemotherapy.
3. To find the effect of drugs.

Pathophysiology

1. White blood cells develop from the stem cells in the bone marrow.
2. Stem cells differentiate:
   1. Granulocytic series cells.
   2. Non-Granulocytic cells.
   3. The granulocytic series consists of:
      1. polymorphonuclear leucocytes (Neutrophils).
      2. Eosinophils.
      3. Basophils.
      4. Monocytes.

White blood cells are divided into:

1. Phagocytic cells:
   1. Polys.
   2. Eosinophils.
   3. Basophils.
   4. Monocytes.
2. Immunocytic cells:
   1. B- lymphocytes.
   2. T-lymphocytes are:
      1. T-helper cells.
      2. T-cytotoxic cells.
      3. T-effector cells.

Preparation of TLC solution:

1. Principle of the TLC method:
   1. Blood is diluted with a fluid that causes the hemolysis of the RBCs but WBCs remain intact and then these are counted in the Neubauer chamber.
   2. Gentian violet lightly stains the leucocytes and allowing those to be counted.
2. Chemicals needed are:
   1. Glacial acetic acid = 2 ml.
   2. Gentian violet (1%) = 1 ml.
   3. Distal water = 97 ml.
   4. This is basically a 2% solution of acetic acid.
   5. Add 2 ml of glacial acid 2 + gentian violet (1 %) 1 ml to 97 ml of distle Water to make up to 100 ml solution.
3. TLC or WBC pipette:
   1. This pipette (also called Thoma pipette) long stem is divided into two parts:
      1. The long stem is marked with 0.5 and 1.0
      2. While the short arm after the bulb is marked 11.
      3. Its central portion is a bulb or a globular shape with one white bead in it.
      4. Rubber tubing is attached to suck the blood.
      5. Ultimately the dilution of the blood to the TLC fluid is 1:20.
         

         WBC pipette

4. Procedure:
5. Take the TLC pipette which has a white bead inside.
6. Fill the blood into the make and then add the TLC solution.
   1. Fill the blood to 0.5 in the pipette.
   2. Fill the pipette with the TLC solution to point 11.
   3. Remove the rubber tubing
   4. Seal both ends or hold in between two fingers.
   5. OR can put this pipette on the mechanical device to shake it.
   6. Shake for 1 minute or preferably for 2 minutes.
   7. Shaking is important before filling the Neubauer chamber.
   8. After thorough mixing, discard the first few drops and then gently fill the chamber until the platform is filled.
   9. The fluid will be drawn by the capillary action.
   10. Allow the chamber on the microscope stage for 2 to 3 minutes, till the cells are settled.
   11. Tube method:
       1. Take 0.02 mL blood and mix it with diluting fluid.
       2. Take TLC dilution fluid 0.38 mL in a small tube and mix it with the blood.
       3. Mix them very well.
       4. This tube method is more accurate than the Thoma pipette technique.
7. In case of low WBC count, fill the pipette to mark 1 and this will give dilution of 1:10, OR
   1. Take 0.1 mL blood and 0.9 mL diluent solution.
   2. In the case of high WBC count, then make higher dilution.
      

      Neubauer chamber

      

      Neubauer chamber counting the WBC labeled WBC

Calculations:

1. Count the cells in the Neubauer chamber. These are counted in the four large corner square labeled as WBC and if the number is Y.
   1. One large area is 1 x 1  mm and depth is 0.1 mm.
   2. Total area counted in 4 large squares = 4 x 1 x o.1 = 0.4 µL (4/10).
   3. Y x 10/4 is the total WBC in the cell in 1 µL.
   4. Now dilution is 1:20.
   5. Number of cells in 1µL = Y x 10 x 20/4 = Y x 50 = Total WBC count.
   6. Total TLC = counted cells Yx 50 =  TLC/cmm.
2. Source of errors are:
   1. If there are microclots in the sample.
   2. If inadequate mixing is done.
   3. Improper filling of the chamber.
   4. If the dilutions are improper.
   5. Mistakes in the calculations.

Normal values of total leucocytes are:

Source 2

• Adult /child = 5000 to 10,000 /cmm
• Child ≤2 years = 6200 to 17000 /cmm.
• Newborn = 9000 to 30,000 /cmm

Other sources

1. At birth            = 10,000 to 25,000/cmm
2. Infants             = 8000 to 15,000/cmm
3. Adults               = 4000 to 10,000/cmm
4. Pregnant ladies =  12,000 to 15,000/cmm

Increased TLC (Leucocytosis) is seen in:

1. Mostly in the case of infections that may be bacterial or viral.
2. In the case of leukemias.
3. After the strenuous exercise.
4. Pain and anorexia.
5. Epileptic seizures.
6. Emotional reaction.
7. Mild leucocytosis in pregnancy.

Decreased leucocytosis (neutropenia) is seen in:

1. This may be seen in fever, malaise, and chills.
2. Infections.
3. Hypersplenism.
4. Deficiency of vitamin B12.
5. Malignant infiltration of the bone marrow.
6. Bone marrow aplasia.
7. Bone marrow depression by radiations.
8. Autoimmune diseases like SLE.

• Critical value = <2500  or >30,000 /cmm.
• Please see for more details in complete blood count (CBC) part 1.

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