Rapid evaluation of malaria parasite density and standardization of thick smear examination for epidemiological investigations
Spencer, T.
Transactions of the Royal Society of Tropical Medicine and Hygiene 80(3): 491
1986
ISSN/ISBN: 0035-9203 PMID: 3798550 Document Number: 274015
Techniques for counting leukocytes in the blood of malarial patients are discussed. A technique which allowed single counts and a calculable degree of precision was the counting of leukocytes in a standard thickness film over a standard area of slide. It allows for leukocyte count and differential counts to be made from the same slide as that used for estimating parasite numbers. This technique was extensively and successfully used, by the author, in Papua New Guinea, using a film thickness of 0.042mm. The practical limit of accuracy was +or-5% for 20 field counts and proportionately greater, up to +or-50%, for 5 field counts on each film. The correspondent comments on the effect of any variability of leucocyte counts upon estimations of malaria parasite density in blood smears. The only method that eliminates this problem is the preparation of a film of a standardized thickness by spreading a measured volume of blood (by micropipette) over a standard area on the slide. An advantage of this method is that leucocyte and differential counts as well as parasite-density estimations can be made on the same smear. The correspondent used the technique extensively during field surveys in Papua New Guinea.Malcolm Guy.