III. Platelets count (Thrombocytes count)
Blood in EDTA anticoagulant is preferred.
Diluting fluid is Rees and Ecker solution
Formaldhyde (40 %)
Brillient cresyl blue
I- Filling the pipette
Diluting fluid is drawn to the mark 1 of the RBC pipette and immediatelly expelled.
Aspirate blood to 0.5 mark of the RBCs diluting pipette.
Aspirate diluting fluid to 101 mark.
Mix blood and diluting fluid mechanically for 5 min.
II- Filling the counting chamber:
Proceed as previously explained in ñRBCs count.
Allow counting chamber to stand for 20-30 minutes to allow the platelets to settle.
To prevent drying out of the preparation, it showed be kept in a moist atmosphere, this is most easily arranged by placing the filled counting chamber in the bottom of a clean Petri dish, along side of which arrange a small piece of cotton wool which has been soaked in water and squeezed out. Petri dish lid is additionally put over the dish.
After 20 -30m the counting chamber can be removed and carefully transferred to the microscope stage.
III- Counting the number of platelets
Focus in the surface of the haemocytometer chamber with the high dry objective. Dim the light to make the thrombocytes visible, and while focussing up and down with the fine adjustment, count all of the thrombocytes in the entire center 1 mm2 (erythrocyte counting area) of both sides of the haemocytometer. This give the number of the thrombocytes in 0.2 µl of 1 : 200 dilution of blood.
The umber of thrombocytes counted X 1000 = number of thrombocytes/µl of undiluted blood