Assessing bleeding risk by thromboelastography when automated platelet count fails due to giant platelets

• Immunofluorescent microscopy demonstrates the presence of circulating megakaryocytes in patients with giant platelets and thrombocytopenia • TEG helps assess the hemostatic function in patient with macrothrombocytopenia and avoids unnecessary platelet transfusion Giant platelets with thrombocytopenia are seen in various conditions, including rare macrothrombocytopenia with high bleeding tendency. An automated hematology analyzer may fail to provide valid platelet count if numerous giant platelets are present, affecting transfusion management. To determine the nature of giant platelets and test if thromboelastography (TEG) may help assess bleeding risk in critically ill patients with an invalid automated platelet count. A DXI 900 hematology analyzer and TEG 5000 are used for complete blood count (CBC) and thromboelastography, respectively. Immunofluorescent staining of the peripheral blood smear with anti-beta 3 IgG was performed to visualize these giant platelets, which were quantified using an automatic software. In past six months, we have performed over 150,000 CBC tests and identified only five patients with a high number of giant platelets, which invalidated automatic platelet counts. The age of these patients varied from 21 to 76 years, and all were critically ill. Despite the low platelet counts in all three patients, TEG parameters were within normal ranges, thus no platelet transfusion was given. Immunofluorescent microscopy demonstrated that most of these giant platelets were in fact megakaryocytes. In conclusion, our results indicate that most circulating giant platelets are megakaryocytes that are potentially functional in supporting hemostasis based on TEG analysis. Thus, TEG may be used to quickly assess the bleeding risk and help guide appropriate transfusion management in thrombocytopenic patients with circulating giant platelets/megakaryocytes