Platelet Count

Platelets play a major role in hemostasis. Both thrombocytopenia and thrombocytosis may be associated with impaired hemostasis. Thrombocytopenia may be defined, as a platelet count below 140, 000/uL, but spontaneous bleeding usually does not occur with counts above 20,000/uL. Thrombocytopenia may be due to one of several mechanisms. Decreased platelet production occurs in aplastic anemia and bone marrow displacement (such as due to leukemia, lymphoma, or carcinoma). Increased peripheral platelet destruction may be secondary to a platelet autoantibody (immune thrombocytopenic purpura), drug-induced immune thrombocytopenia, DIC, or thrombotic thrombocytopenic purpura. Ineffective thrombopoiesis results in thrombocytopenia associated with megaloblastic anemia.

Thrombocytosis (a platelet count > 400,000/uL) may occur secondary to infection, inflammation, malignancy, hemorrhage, surgery, splenectomy or iron deficiency. Thrombocytosis is also commonly associated with abnormal platelet morphology and function.

Reference range is 140,000 - 400,000/uL. Platelet counts <30,000/uL and >1 million/uL are considered critical values.

Specimen requirement is one lavender top (EDTA) tube of blood.

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