Platelets, also called thrombocytes, are the smallest cells in the blood. These cells do not have a nucleus, are round or oval, flattened, disk-shaped structures, and are necessary for coagulation. Two tests that measure or count the number of platelets are the platelet count, which measures the number of platelets in the blood, and the mean platelet volume (MPV), which provides information about platelet size.
A platelet count test often follows a decreased platelet count that was estimated from a peripheral blood smear . The platelet count is an important blood test because thrombocytopenia is the most common cause of bleeding diseases. This count is used to evaluate bleeding disorders due to liver disease, thrombocytopenia, and anticoagulant therapy . The test is also ordered for patients who have diseases associated with bone marrow problems, such as leukemia and aplastic anemia . The platelet count is expressed as the number of platelets per cubic millimeter (mm3) of blood.
An abnormal increase in the number of platelets is called thrombocythemia or thrombocytosis. This increase is seen in diseases such as malignancies, early stages of chronic granulocytic leukemia, polycythemia vera, tuberculosis, chronic inflammatory disease, and chronic blood loss.
A decreased platelet count is known as thrombocytopenia and can result in significant bleeding problems . Diseases that decrease the platelet count include pernicious and aplastic anemias, and idiopathic thrombocytopenic purpura (ITP). A low platelet count is commonly seen in AIDS cases. Exposure to various chemicals and the toxic effects of many drugs can also lead to thrombocytopenia. Individuals who have serious platelet deficits often show signs or symptoms such as petechiae, bleeding from gums, nosebleeds, and gastrointestinal bleeding.
Interfering Circumstances. Platelet counts can show a normal increase at high altitudes, after strenuous exercise, and in the winter. A normal decrease occurs on the first day of an infant's life and before menstruation.
Normal Range Platelets
150,000-400,000/mm3