Endomitotic index of megakaryocytes measured by flow cytometry helps to diagnose hematological disorders with abnormal platelet counts.

Platelet production is a regulated phenomenon. Indeed, megakaryocyte volume is inversely correlated to the platelet count not only in normal individuals and immune thrombocytopenic purpura patients, but also, and surprisingly, in chronic myeloid leukemia patients. Patients with polycythemia vera and essential thrombocythemia are located outside this regression line. Herein, we describe morphometrical data confirmed by the flow cytometric measurement of the megakaryocyte endomitotic index (EI). The EI is a value which reflects the mean ploidy of megakaryocytes and corresponds to the mean of (¿log2 DNA content expressed in N¿-1). In this study, the megakaryocyte endomitotic index of 14 normal individuals was compared to those of chronic myeloid leukemia (CML) patients (n = 16), immune thrombocytopenic purpura (ITP) patients (n = 11), essential thrombocythemia (ET) patients (n = 10) and polycythemia vera (PV) patients (n = 12). The megakaryocyte EI was significantly lower in CML patients than in normal individuals. In contrast, in ET, PV and ITP patients, megakaryocyte EI was higher than in normal individuals. An inverse relationship between the endomitotic index estimated by flow cytometry and the mean megakaryocyte volume performed by morphometry was observed in normal individuals, CML and ITP patients. In conclusion, the endomitotic index is higher in ITP, ET and PV patients and lower in CML patients when compared to normal individuals and is an interesting tool which can help to diagnose rapidly hematological disorders with abnormal platelet counts.