A WBC count is a blood test to measure the number of white blood cells (WBCs) in the blood. White blood cells (WBCs), are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders.
White blood cells (or leukocytes) are divided into two main groups: granulocytes and agranulocytes. The granulocytes receive their name from the distinctive granules that are present in the cytoplasm of neutrophils, basophils, and eosinophils. However, each of these cells also contains a multilobed nucleus, which accounts for their also being called polymorphonuclear leukocytes. In laboratory terminology, they are often called “polys” or PMNs. The nongranulocytes, which consist of the lymphocytes and monocytes, do not contain distinctive granules and have nonlobular nuclei that are not necessarily spherical. The term mononuclear leukocytes is applied to these cells.
The endocrine system is an important regulator of the number of leukocytes in the blood. Hormones affect the production of leukocytes in the blood-forming organs, their storage and release from the tissue, and their disintegration. A local inflammatory process exerts a definite chemical effect on the mobilization of leukocytes. The life span of leukocytes varies from 13 to 20 days, after which the cells are destroyed in the lymphatic system; many are excreted from the body in fecal matter. Leukocytes fight infection and defend the body by a process called phagocytosis, in which the leukocytes actually encapsulate foreign organisms and destroy them. Leukocytes also produce, transport, and distribute antibodies as part of the immune response to a foreign substance (antigen).
The WBC serves as a useful guide to the severity of the disease process. Specific patterns of leukocyte response can be expected in various types of diseases as determined by the differential count (percentages of the different types of leukocytes). Leukocyte and differential counts, by themselves, are of little value as aids to diagnosis unless the results are related to the clinical condition of the patient—only then is a correct and useful interpretation possible. Signs and symptoms of increased WBCs include fever, bruising, petechiae, fatigue, anemia, bleeding of mucous membranes, weight loss, and history of infections.
UNITS OF MEASURE VARIATIONS FOR WHITE BLOOD CELL COUNT (WBC) USED IN LABORATORY REPORTS
| thousand cells per microliter (µL) = thousand cells per cubic millimeter (mm3) |
| cells per microliter (µL) = cells per cubic millimeter (mm3) |
THOUSAND CELLS PER MICROLITER (µL). A unit of cell concentration expressed as a number of cells in thousands per unit volume equal to one microliter.
| thousand/microliter | thousands/µL | thousands/mcL | thousands/uL |
| thous/microliter | thous/µL | thous/mcL | thous/uL |
| thou/microliter | thou/µL | thou/mcL | thou/uL |
| th/microliter | th/µL | th/mcL | th/uL |
| 1000/microliter | 1000/µL | 1000/mcL | 1000/uL |
| 10^3/microliter | 10^3/µL | 10^3/mcL | 10^3/uL |
| 103/microliter | 103/µL | 103/mcL | 103/uL |
| K/microliter | K/µL | K/mcL | K/uL |
THOUSAND CELLS PER CUBIC MILLIMETER (mm3). A unit of cell concentration expressed as a number of cells in thousands per unit volume equal to one cubic millimeter.
| Thousand/cubic millimeter | thousands/mm3 | thousands/mm^3 | thousands/ cmm | thousands/cumm | thousands/cu mm |
| Thous/cubic millimeter | thous/mm3 | thous/mm^3 | thous/cmm | thous/cumm | thous/cu mm |
| Thou/cubic millimeter | thou/mm3 | thou/mm^3 | thou/cmm | thou/cumm | thou/cu mm |
| Th/cubic millimeter | th/mm3 | th/mm^3 | th/cmm | th/cumm | th/cu mm |
| 1000/cubic millimeter | 1000/mm3 | 1000/mm^3 | 1000/cmm | 1000/cumm | 1000/cu mm |
| 10^3/cubic millimeter | 10^3/mm3 | 10^3/mm^3 | 10^3/cmm | 10^3/cumm | 10^3/cu mm |
| 103/cubic millimeter | 103/mm3 | 103/mm^3 | 103/cmm | 103/cumm | 103/cu mm |
| K/cubic millimeter | K/mm3 | K/mm^3 | K/cmm | K/cumm | K/cu mm |
CELLS PER MICROLITER (µL). A unit of cell concentration expressed as a number of cells per unit volume equal to one microliter.
| cells /microliter | cells /µL | cells /mcL | cells /uL |
| /microliter | /µL | /mcL | /uL |
| microliter | µL | mcL | uL |
CELLS PER CUBIC MILLIMETER (mm3). A unit of cell concentration expressed as a number of cells per unit volume equal to one cubic millimeter.
| cells/cubic millimeter | cells/mm3 | cells/mm^3 | cells/cmm | cells/cumm | cells/cu mm |
| /cubic millimeter | /mm3 | /mm^3 | /cmm | /cumm | /cu mm |
| cubic millimeter | mm3 | mm^3 | cmm | cumm | cu mm |