Determination of Platelet Count

AIM: Determination of Platelet Count (Thrombocyte)

Principle

• The total platelet count is a blood test used to measure the number of platelets (thrombocytes) in the blood.
• Platelets are crucial for blood clotting and wound healing.
• The count is usually performed using an automated blood cell analyzer or a manual method with a hemocytometer.
• The procedure involves diluting a blood sample and counting the platelets under a microscope or via automated machinery, which calculates the total number of platelets per microliter (µL) of blood.

---

Requirements

1. Whole blood EDTA

2. Hemocytometer

3. Hemocytometer (counting chamber)

4. Pipettes

5. Glass slides

6. Cover slips

7. Microscope
8. Diluting fluid: –
   • Procaine – 3.0 g
   • Sodium hydrochloride – 10 g
   • Distilled water – 100 ml

---

Procedure

1. Prepare a dilution fluid.  
2. Dilute the blood sample with the dilution fluid in a known ratio.
3. By using an RBC pipette, draw blood up to the 0.5 mark.
4. Wipe excess blood on the outside of the pipette.
5. The diluting fluid is drawn up to mark 101 (blood is diluted 1:200).
6. Mix the contents in the bulb thoroughly.
7. After 5 minutes, discard the first drop, then transfer a small drop to one side of the counting chamber.
8. Place, he filled a mounted counting chamber under a petri dish with a moist filter paper. Let it stay undisturbed for l5 minutes.
9. Place the counting chamber carefully on the stage of the microscope. Under low power magnification, focus red cell counting area.
10. Move to view the chamber square of the red cell area and change to a high-power objective.
11. Keep the condenser down and reduce the light by adjusting the diaphragm.
12. The platelets will appear like highly refractile particles.
13. Count platelets in all 25 small squares. The area covered by 25 squares is equivalent to I square mm.
14.  Calculation:

    • Use the formula to calculate the total platelet count based on the number of platelets counted, dilution factor, and the volume of the hemocytometer.

Platelet count (per µl) = Number of platelets counted × Dilution /Volume of fluid

---

---

Normal Range

Normal Platelet Count: 150,000 to 450,000 platelets per microliter (µL) of blood.

Clinical Significance

Low Platelet Count (Thrombocytopenia):

• Platelet Count: Below 150,000 platelets/µL.

• Causes:

  • Bone marrow disorders (e.g., leukemia, aplastic anemia).

  • Autoimmune diseases (e.g., lupus, immune thrombocytopenic purpura [ITP]).

  • Viral infections (e.g., dengue, HIV).

  • Drug-induced (e.g., heparin-induced thrombocytopenia).

  • Blood loss or dilution (e.g., after massive transfusion).

  • Liver diseases (e.g., cirrhosis).

• Symptoms:

  • Increased risk of bleeding (e.g., easy bruising, petechiae, gum bleeding).

  • Prolonged bleeding after injury or surgery.

---

High Platelet Count (Thrombocytosis):

• Platelet Count: Above 450,000 platelets/µL.

• Causes:

  • Reactive (secondary) thrombocytosis due to infections, inflammation, or iron deficiency.

  • Essential thrombocythemia (a type of myeloproliferative disorder).

  • Chronic myelogenous leukemia (CML).

• Symptoms:

  • Risk of abnormal blood clot formation, leading to conditions like stroke, deep vein thrombosis (DVT), or pulmonary embolism.

  • Can be asymptomatic, but in some cases, patients may have headaches, dizziness, or vision disturbances.

---

Monitoring Disease Progression and Treatment:

• Platelet count is used to monitor conditions such as:

  • Cancer treatments (chemotherapy, radiotherapy) that may affect platelet production.

  • Liver cirrhosis, where platelet count can reflect the degree of disease progression.

  • Bone marrow disorders, where changes in platelet count may indicate response to treatment.