It is difficult to identify the species of the parasite on a thick film, although it may be possible to do so by an experienced microscopist. An inexperienced microscopist may misidentify platelets for parasites as these can be found in abundance in the thick film without any relation to the red cells. Examination of thin blood films Ideally the tail end of the slide, where the red cells are separated to a layer one cell thick, should be examined. The thin film is examined under oil immersion x100 objective microscopy. On a well stained slide red cells appear pale straw to light grey in colour, leucocytes have dark blue or purple nuclei with light blue cytoplasm.
Platelets appear blue or purple.
Species identification can be aided by studying the red cells containing the malaria parasites, noting their size, shape and the presence or absence of stippling. P. ovale, on the other hand, is diagnosed by the presence of trophozoites in the enlarged red blood cells which may be oval in shape with or without fimbriation and contains Jame's dots. It is important to remember that the stippling may not be present in red cells infected with young ring forms of P. vivax and P. ovale. In P. malariae, infection the infected red cells appear to be smaller than normal and contain a thick, compact and densely staining trophozoite. In later stages the cells usually contain coarse yellow-brown pigment.