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How Looking at Cells Under a Microscope Aids in Medical Diagnosis

written by: Teresa Martin•edited by: Diana Cooper•updated: 3/18/2011

Tiny cells under a microscope provide invaluable information for diagnosing diseases. There are clues in the appearance of both red blood cells and white blood cells that aid in diagnosing mononucleosis, anemia and the probable cause for infection.

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    Much of medical diagnostics involves looking at cells under a microscope. This provides invaluable information about the condition of the body. Many diseases are noted by appearance of cells or an increase or decrease in normal values. Consider for example, a CBC, or complete blood count. The CBC provides information about the quantity of red blood cells, white blood cells and platelets. It also gives the concentration of hemoglobin and the percentage of cells in the total blood volume.

    When a technologist or physician looks at cells under a microscope, further information is gained. The appearance of red blood cells can indicate whether or not anemia is present and if so, what type of anemia. The percentage of white blood cells and the distribution of neutrophils, lymphocytes, monocytes and other cells also provides valuable information regarding the presence of a bacterial or viral infection or mononucleosis.

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    Anemia is due to a decrease in blood volume, an inability to produce new red blood cells, or a genetic condition. When looking at red blood cells under a microscope, the technologist looks for hypochromia, which is a decrease in the amount of hemoglobin in each cell. The red blood cells, which normally have a small area of pallor in the center will have a larger area of central pallor. In very severe cases of anemia the cells may appear as a rim of red around a large area of white. Even in the presence of a large amount of cells, if there is severe hypochromia, this correlates with a decrease in hemoglobin and anemic conditions.

    The technologist will also observe the appearance of the red blood cells. Generally the cells are round, however, under some conditions the shape may be altered. If the cells are fragmented, there is possibly a condition in the body that is tearing the cells. This could be due to DIC or disseminated intravascular coagulation. In this disease, there is fibrin that is being formed in the body which interferes with the movement of blood cells through the capillaries. Some of the cells become torn as they move through vessels and appear like "helmets" because of the manner in which the cells are usually torn.

    There are genetic conditions that can be identified and viewed by looking at cells under a microscope. Cells with a sickle like appearance are long and may be slightly curved. Red blood cells that appear like a target, with a central area of color surrounded by a circle of white around it giving the cells the appearance of a target. These result from a hemoglobin disease that is genetically based, liver disease or splenectomy.

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    Infection - Bacterial or Viral

    Not feeling well? There may be an infection somewhere in the body. It could be from a bacteria or a virus. The best way to know is through a differential. A CBC often includes a differential, which is a breakdown of the percentage of the types of white blood cells. Normally there are more neutrophils than lymphocytes. The normal range in a differential for neutrophils is 40-60% and for lymphocytes 20-40% with the remainder made up from a variety of other white bloods cells.

    Looking at the cells under a microscope and counting them can give an indication of the percentage and abnormalities within the white blood cells. If the neutrophils are increased and there is a corresponding increase in immature neutrophils, called neutrophilic bands, this indicates an infection caused by bacteria. If there is a increase in lymphocytes then the infection is more likely due to a virus.

    Lymphocytes can also appear abnormal. Atypical lymphocytes are just that, atypical appearing lymphocytes. These are a larger amount of cytoplasm which is easily indented by red blood cells around them. After staining with Wright's stain, the edges of atypical lymphocytes can appear to have purple staining their edges. Atypical lymphocytes are present in mononucleosis. Their presence along with a mono test are the diagnostic tools for mono.

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