Malaria
is diagnosed by microscopic examination of the blood. Thick
and thin blood films are made on clean, grease – free glass
slides. Having written the patient’s name, time and date,
the glass slide can be cleaned by breathing on the surface and
wiping with a clean cloth.
Method
in detail
Third finger of the left hand of the patient should be
held with left hand between thumb and finger by blood slide
collector at the first phalangeal joint.
Wipe finger tip with swab dipped in spirit or Savlon solution
Allow the fingertip to dry
Hold the pricking needle in the right hand and prick the
finger
Allow blood drop to ooze out
Take a clean slide
Take three drops of blood (sufficient blood) 1 cm from
the edge of the glass slide
Take another drop of blood 1 cm from the first drop of
blood
Take another slide with smooth edge and use it as spreader
Make thick and thin smears
Allow it to dry
Put the slide identification number/ name on thin smear
with lead pencil
Making good thin films requires practice. Anemic blood smears
poorly. The thick film should be stirred in a circular motion
with the corner of the second slide until clotting takes
place. The thick film must be of uneven thickness, but it
should be possible to read the hands, but not the figures,
of a watch face through the film.
The thin blood smear should be air-dried rapidly, fixed
in anhydrous methanol, stained and the red cells in the
tail of the film should be examined under oil immersion.
The level of parasitaemia is expressed as number of parasitized
erythrocytes among thousand cells and this figure is then
converted to the number of parasitized erythrocytes per
microliter.
The thin blood smear should be dried thoroughly and stained
without fixing. Both parasites and white cells are counted,
and the number of parasites per unit volume is calculated
from the total leukocyte count.
