is essential and the percentage parasitaemia should always be reported as this has implications for prognosis and the pattern of treatment employed. Method 1
a. Air dry thin films
b. Fix in methanol for 1 minute
c. Wash in tap water and flood the slide with Giemsa (see appendix for details of manufacturer) diluted 1 in 10 with
buffered distilled water pH 7.2. The diluted stain must be freshly prepared each time.
d. Stain for 25 - 30 minutes.
e. Run tap water on to the slide to float off the stain and to
prevent deposition of precipitate on to the film.
f. Drain slide vertically and leave to dry.
g. Examine the section of the film where the red cells are one layer thick and touching,
using the x100 objective.
The recommended procedure for estimating the percentage parasitaemia in a thin blood film is by expressing the number of infected cells as a percentage of the red blood cells e.g. 3 parasitised red
cells/100 red blood cells or 3% parasitaemia.
A red blood cell infected with multiple parasites counts as one parasitised red cell.
The percentage parasitaemia should be calculated by
counting the number of parasitised red cells in 1000 cells in a thin blood film.
Method 2
Alternatively the World Health Organisation recommend a method which compares the number of
parasites in a thick blood film with the white blood cell count.
The parasitaemia is estimated by first counting the number of parasites per 200 white blood cells in a thick blood film and then
calculating the parasite count/
