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.

- A thick blood smear is a drop of blood on a glass slide. Thick blood smears are most useful for detecting the presence of parasites, because they examine a larger sample of blood. (Often there are few parasites in the blood at the time the test is done).
- A thin blood smear is a drop of blood that is spread across a large area of the slide. Thin blood smears help providers discover what species of malaria is causing the infection.
- The two smears can work in tandem if a thick and thin smear is made. This method allows the provider to observe both thick and thin smears and find the blood density that is most likely to yield visualization of the parasite to the given observer.
- If a high index of suspicion exists for malaria in a given patient, but microscopy does not reveal an obvious malarial infection, serial thick and thin smears can be repeated every 8 or 24 hours depending on the severity of the case.