First Quarter 2008 - Issues in Hematology - ION Solutions

oncologistics thrombocytopeniaGAMUT OF POSSIBILITIESby: Charles S. Abrams, M.D.Hemorrhage following trauma or surgery generallydoes not occur if the platelet count is morethan 50,000/µL. In an otherwise hemostaticallynormal patient, signifi cant spontaneous bleedingtypically does not occur with a platelet count ofgreater than 5,000-10,000/µL. However, there isno absolute threshold for spontaneous bleedingdue to thrombocytopenia. It may occur at highercounts when fever, sepsis, severe anemia, andother hemostatic defects are present, or whenplatelet function is impaired by medication. Notably,a prolonged cutaneous bleeding time does notaccurately predict clinical bleeding. Therefore,it is critical that the physician run the gamut ofpossibilities when diagnosing the cause of a lowplatelet count. Thrombocytopenia can be due toaccelerated platelet removal, decreased plateletproduction by bone marrow megakaryocytes, or byplatelet sequestration in an enlarged spleen. Sincethere is no easy test to differentiate among thesepossibilities, clinical evaluation is critical.The rubric of diagnosis for any condition entails the physiciantaking a detailed history. Additionally, a thorough physicalexamination, with attention to possible alternative explanationsfor thrombocytopenia must be performed. This is especiallyimportant for thrombocytopenia, because some causes suchas idiopathic thrombocytopenic purpura (ITP) remain thediagnosis of exclusion. In addition, a complete blood count witha differential is mandatory, as is the examination of the peripheralblood smear. Other tests may also be warranted based upononcologistics 17