A blood smear, peripheral blood smear or blood film is a thin layer of blood smeared on a glass microscope slide and then stained in such a way as to allow the various blood cells to be examined microscopically. Blood smears are examined in the investigation of hematological (blood) disorders and are routinely employed to look for blood parasites, such as those of malaria and filariasis.
Malaria is a mosquito-borne infectious disease that affects vertebrates and Anopheles mosquitoes. Human malaria causes symptoms that typically include fever, fatigue, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. Symptoms usually begin 10 to 15 days after being bitten by an infected Anopheles mosquito. If not properly treated, people may have recurrences of the disease months later. In those who have recently survived an infection, reinfection usually causes milder symptoms. This partial resistance disappears over months to years if the person has no continuing exposure to malaria. The mosquitoes themselves are harmed by malaria, causing reduced lifespans in those infected by it.
Malaria is caused by single-celled eukaryotes of the genus Plasmodium. In mammals, it is spread through bites of infected female Anopheles mosquitoes. The mosquito bite introduces the parasites from the mosquito's saliva into the blood. The parasites travel to the liver, where they mature and reproduce. Five species of Plasmodium commonly infect humans. The three species associated with more severe cases are P. falciparum (which is responsible for the vast majority of malaria deaths), P. vivax, and P. knowlesi (a simian malaria that spills over into thousands of people a year). P. ovale and P. malariae generally cause a milder form of malaria. Malaria is typically diagnosed by the microscopic examination of blood using blood films, or with antigen-based rapid diagnostic tests. Methods that use the polymerase chain reaction to detect the parasite's DNA have been developed, but they are not widely used in areas where malaria is common, due to their cost and complexity.
Malaria antigen detection tests are a group of commercially available rapid diagnostic tests of the rapid antigen test type that allow quick diagnosis of malaria by people who are not otherwise skilled in traditional laboratory techniques for diagnosing malaria or in situations where such equipment is not available. There are currently over 20 such tests commercially available (WHO product testing 2008). The first malaria antigen suitable as target for such a test was a soluble glycolytic enzyme Glutamate dehydrogenase.None of the rapid tests are currently as sensitive as a thick blood film, nor as cheap. A major drawback in the use of all current dipstick methods is that the result is essentially qualitative. In many endemic areas of tropical Africa, however, the quantitative assessment of parasitaemia is important, as a large percentage of the population will test positive in any qualitative assay.
In immunology, agranulocytes (also known as nongranulocytes or mononuclear leukocytes) are one of the two types of leukocytes (white blood cells), the other type being granulocytes. Agranular cells are noted by the absence of granules in their cytoplasm, which distinguishes them from granulocytes. Leukocytes are the first level of protection against disease. The two types of agranulocytes in the blood circulation are lymphocytes and monocytes. These make up about 35% of the hematologic blood values.
The distinction between granulocytes and agranulocytes is not useful for several reasons. First, monocytes contain granules, which tend to be fine and weakly stained (see monocyte entry). Second, monocytes and the granulocytes are closely related cell types developmentally, physiologically and functionally. Third, this distinction is not used by haematologists; it is an erroneous separation that has no meaning.
Romanowsky staining is a prototypical staining technique that was the forerunner of several distinct but similar stains widely used in hematology (the study of blood) and cytopathology (the study of diseased cells). Romanowsky-type stains are used to differentiate cells for microscopic examination in pathological specimens, especially blood and bone marrow films, and to detect parasites such as malaria within the blood.
The staining technique is named after the Russian physician Dmitri Leonidovich Romanowsky (1861–1921), who was one of the first to recognize its potential for use as a blood stain.