Platelet Count (Manual Method)

PLATELET COUNT (Manual Method)

PLATELET COUNT (Manual Method):-

Principle Platelets are difficult to count because :-

1. They agglutinate, fragment and break down readily and quickly.

 2. Because of their small size they are hard to differentiate from debris.

 3. They adhere to glass.

 4. Platelets are not evenly distributed throughout the blood and have a tendency to clump together. The diluent used haemolyses the red cells leaving the white cells and the platelets intact.

Blood specimen:- is collected taking care that the platelets do not clump. Whole blood is diluted appropriately using a diluent which haemolyses red cells. The platelets are then counted in a counting chamber. Specimen Venous blood should be collected in a tube containing EDTA as an anti-coagulant (2 mg/ml of blood). The EDTA also prevents clumping of platelets. Blood collected by finger prick should not be used because platelets are probably lost at the site of skin puncture.

Diluting fluids:-

1. Formal citrate fluid: Prepare 31.3 g perlitre solution of trisodium citrate. Add 1 ml of formalin to 99 ml of the citrate solution.

2. Ammonium oxalate: 10 g per litre (1 %). Prepare freshly just before use.

Technique Prepare 1:200 dilution of the blood using the diluting fluid in a Thoma pipette. Alternatively, add 0.02ml of blood to 3.98ml of diluting fluid. Charge the new board chamber

count the total number of platelets suing a high power (40 x) o bjcective in the four large corner squares (4mm)

Normal range:- Adult: 150.000 -400.000cu.mm (150 to 400× 10⁹/L)