Blood smear and its preparation

   What is blood smear?

It is a thin film of blood on slide, that after staining is used to examine mainly the morphology of blood cells.

Why we make and examine blood smears?

We make and examine or investigate smear because  from its examination we can get following useful information:

a.      a. A leukocyte estimate RBC & platelet morphology

b.      b. A 100-cell leukocyte differential Observation for the presence of abnormal Cell.

c.      c. Abnormal RBC distribution, platelet estimate Malarial parasite.

d.    d.  It help us in screening of illness and diagnosis of hematologic & non-hematologic conditions.

e.     e. It also help us to monitor patient response to therapy.

BLOOD SMEAR TYPES

There are two types of smear on base of method of preparation;

1.Spun smear

2.The wedge smear.

There are two additional types of blood smear (On base of their composition) used for specific purposes:

1.Buffy coat smear for WBCs<1.0×109/L

2.Thick blood smears for blood parasites.

1.WEDGE SMEAR :

It is most common, widely used  and preferable method. Lab workers make it by hands, using slides. It is easy to be labelled .

WEDGE SMEAR PREPARATION:

a.     a. A drop of blood is applied on slide, through capillary tube, near an end od slide.

b.     b. Spreader commonly a second slide is draw back toward drop of blood and held there for some time until blood spread to its width.

c.     c. Now the spreader at 45 degree, is pushed forward to produce a long thin and even smear or film of blood.

 CHARACTERISTICS OF A GOOD BLOOD FILM:-

1.Thick at one end, thinning out to a smooth rounded feather edge.

2.Should occupy 2/3 of the total slide area (min. length of 2.5cm)

3.Should not touch any edge of the slide.

4.Should be margin free, except for point of application5.No streaks, waves or troughs

2. SPUN METHOD OF SMEAR FORMATION:

It is an automated method . Here we produce a perfect smear by using a specific machine. Commonly Beckman Coulter Gen.SCell is used.

Preparation of smear through spun method:

a.      a. 1-2 drops of blood placed in are of glass slide.

b.      b.The   briefly spun at high speed in a special centrifuge.

c.       c.Blood spreads on slide in a monolayer Leukocytes & platelets are distributed uniformly & free of distortion. RBC  show tendency to distort •Bio hazardous (aerosols)