platelets are small round, oval or

rod-shaped with azurophilic

granules seen in their cytoplasm

With certain anticoagulants

(oxalates) and at temperatures

below 37 degrees Celsius = there’s

a rapid mark platelet swelling.

• Accelerated platelet destruction –

will cause platelet anisocytosis

(variation in size – macrocytosis).

In myelofibrosis, hemorrhagic

thrombocythemia, and in

polycythemia vera – it causes large

and bizarre platelets.

Platelets are counted in relation to

1,000 RBCs in the blood smear.

• Not so reliable since results depend

on the distribution of platelets and

on the RBC count.

• However, the advantage is that it

allows study of platelet

morphology.

Rees-Ecker

Diluent – does not lyse RBC and

WBC.

1. Brilliant cresyl blue (BCB)

2. Sodium citrate – 0.4 g (prevents

clumping of platelets)

3. Formalin – 3 drops in 1:10

dilution (preservative)

4. Sucrose

NORMAL VALUE:

500,000 – 900,000/mm3

14% MgSO4

(Magnesium Sulfate) – does not lyse

RBCs

NORMAL VALUE

250,000-500,000/mm3

uses Brilliant cresyl blue.

• The best method in indirect procedure

but somewhat cumbersome.

• Normal Value:

437,000 – 586,000/mm3

Whole blood is diluted with

platelet diluting fluid in an RBC

pipet and counted in a

hemocytometer.

REES-ECKER

DILUENT – does not lyse RBC and

WBC

a. Brilliant Cresyl Blue – 0.15g

(dye)

b. Sodium Citrate – 0.4g (prevents

clumping of platelets)

c. Formalin – 3 drops of 1:10

dilution (preservative)

NORMAL VALUE

140,000 – 340,000/mm3

DILUTING FLUID:

1. Crystal violet – 0.05g (dye)

2. Sodium citrate – 1.6g

(prevents clumping of

platelets)

3. Formalin (40%) – 94.0 mL

(preservative)

NORMAL VALUE

140,000-340,000/MM3

• DILUTING FLUID: 1% Ammonium

oxalate (lyses RBC).

• The reference method that uses

phase-contrast microscopy with

green (platelets appear dark) or

gray filter (platelets appear pink or

purple). It also uses a flat-bottomed

hemocytometer whose focus can be

easily adjusted and a thin coverslip.

Normal values: 150,000 – 450,000/mm3

Consists of:

1. Reservoir (Diluting fluid):

a. NH4 oxalate

b. Thimerosal (preservative)

2. Capillary pipette

3. Protective shield

NORMAL VALUE

145,000 – 375,000/mm3

whole blood is

collected in EDTA and is

centrifuged briefly to separate

cells from the plasma. The

platelets in the supernatant

platelet-rich plasma are then

counted by means of an

electronic particle counter.

• Example:

1. Bull et. Al. method

Blood samples are

collected in EDTA, diluted and

hemolyzed in 2M urea and

platelets are counted by means

of:

A. Optical particle counter

(employing the principle of

reverse darkfield

microscopy)

B. Electronic aperture counter

• Examples:

1. Hemalog Autoanalyzer

2. Coulter Counter

3. AutoCounter System

4. ThromboCounter