MICROSCOPY
When done correctly, microscopic examination of thick and thin blood smears is the most reliable test for malaria. Blood smears are taken most often from a finger prick and a few drops of blood. Thick and thin blood smears allow direct visualization of parasites and their reproductive derivatives – schizonts in malaria. See U.S. Department of Defense. Special Operations Forces Medical Handbook. 2011.
The thick and thin film should be air-dried, fixed with 100% (absolute) methanol, and allowed to dry before staining with 7.5% Giemsa stain for 15 minutes. Plasmodium parasites are always intracellular, and they demonstrate, if stained correctly, blue cytoplasm with a red chromatin dot (see images 1-4 below). Common errors in reading malaria films can be caused by platelets overlying a red blood cell, concern regarding missing a positive slide, and misreading of artifacts as parasites. The slide is best read by starting at the thin end of the slide and moving it towards the thick side until the RBCs are side by side, but NOT overlapping. This will give the observer the highest concentration of RBCs in view, giving him or her the highest probability of identifying the parasite. Move the slide along this plane of side-by-side RBCs to accurately rule out or in a malarial parasitic infection (Image 1). If the malaria parasite is identified, begin appropriate anti-malaria/anti-parasite treatment immediately in conjunction with the antibiotic therapies (minimum, better, best) mentioned above.