Establishing the etiology of thrombocytopenia.

Hemostasis is dependent on an adequate number of well-functioning platelets in the circulating blood. As the number of circulating platelets decreases, the chance of bleeding increases. Thrombocytopenia, a platelet count of less than 150,000 per microliter, is a laboratory finding and not a diagnosis. Therefore, once thrombocytopenia is identified, a detailed history, physical examination, and further laboratory tests are used to establish an etiology. This article reviews the assessment, diagnosis, and treatment of thrombocytopenia.