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Platelets
are the smallest blood cells in blood circulation , they participate in the bone
marrow . Enumaration of platelets are requested in the investigation of
bleeding disorder.
Specimen :-
EDTA
anti coagulated blood the count must be
completed within 2 hr after blood Collection
Reagent : -
1) Platelet diluting
fluid
a)
Tri
sodium Citrate – 3.8 g.
Na3 c6 H5
O7 2H2O ( 0.106 m)
b)
Neutral
formal dehyde (40%) 2 ml
Brilliant
Cresyl blue - 0-1 g
Distilled
water (q.s) - 100 ml
All are mixed together
filtered Centrifuged and transferred to a tight – stoppered bottome for
refrigeration before use the diluting fluid must be filtered
Equipment
1)
Hemocytometer
withy cover slip.
2)
Sahli’s
pipette (20 micro liter )
3)
Petri
dish with filter paper
4)
Microscope
Procedure
1) 3.98 ml of freshly
filtered diluents is taken in a tube.
2) 0.02 ml of well mixed
anti coagulated blood is added in to the tube.
3) The contain of the
tube is mixed well for at least 5 minutes.
4) A drop of the diluted
specimen is transferred on each side of the counting chamber by the use of
sahli’s pipette.
5) The mounted
hemocytometer is placed inside a moister chamber and left to stay undisturbed
for 15 minutes. This permits the platelet to settle and the moist chamber
prevents evaration of fluid from the hemocyto meter chamber
6) The hemocytometer is
placed on the stage of the microscope focused the RBC counting area.
7) Platelet are bluish
and must be distinguished from debris. They are oval round or comma shaped refractive
bodies that very in size normally 1-5
micro meter.
8) The platelet’s are counter of each side of the
chamber and average counts of two side are taken
9) Finally the number of
platelets are calculated
No of platelet X Dilution
No
platelet (micro liter) = -----------------------------------------
Depth of Fluid
Dilution
So,
the factor = -----------------------------------------
Depth of fluid
Dilution
= -------------------------------
Volume
of fluid
200
= ------------------------
0.01
= 2000
So,
the formula is No of platelets (micro
liter )
No of platelet counted in 5 square X
2000.