PLATELET Count (PLT) Blood
Clinical significance : –
Determination of platelets is requested in the investigation of bleeding disorders . Thrombocytopenia ( decreased platelets count ) is often associated with prolonged bleeding and poor clot retraction .It also occurs in Aplastic anemia , Megaloblastic anemia , hypersplenism , acute leukemia and in immune thrombocytopenia . Thrombocytopenia vera , following splenectomy and in chronic myelogenous leukemia .
Normal range : –
| Male Female | 250,000 – 5000, 000 mm ( microlitter ) |
Specimen : –
EDTA Anticoagulant blood ( fasting not necessary ) . A plastic syringe is preferred for blood collection ( since platelets adhere to glass surface ) . Capillary blood also can be used . It gives lower results compared to venous blood .
Requirements : –
1 Microscope
2 Improve Neubauer counting chamber
3 RBC pipette
4 Platelets diluting fluid
It is prepared as follows
a ) Procaine hydrochloride – 3 . 0 g
b ) sodium chloride – 10 g
c ) Distilled water to – 100 ml
Additional information : –
1 . 3 % ( w / v ) sodium citrate containing 1% ( v /v ) formalin also can be used as diluting fluid . It however , does not lyse the red cell .
2 . Procaine hydrochloride diluting fluid partially lyses the red blood cells . The other diluting fluid which lyses the red cells is 1 % ( w/v ) ammonium oxalate .
Procedure :-
- Mix the blood specimen carefully .
- By using RBC pipette draw blood up to 0. 5 mark .
- Wipe excess blood on the outside of the pipette .
- The diluting fluid is drawn up to mark 101 ( blood is diluted 1: 200 ) .
- Mix the contents in the bulb thoroughly .
- After 5 minutes , discard the first drop then transfer a small drop on one side of the counting chamber .
- Place the filled mounted couting chamber under a Petri dish with a mosit filter paper . Let it stay undisturbed for 15 minutes ( This permits the platelets to settle and also prevents evaporation of diluting fluid in the chamber ) .
- Place the counting chamber carefully on the stage of the microscope . Under low power magnification focus red cell counting area . Move to view the corner square of the red cell area and change to high power objective .
- Keep the condenser down and reduce the light by abjusting the diaphragm . The Platelets will appear like highly refractile particles .
- Count platelets in all 25 small squares . The area covered by 25 squares to 1 sq. mm .
Calculation : –
Platelets per Cumm ( microlitter ) = Number of platelets counted × Dilution / volume of fluid