EVALUATION OF THE CORRELATION BETWEEN JAK2V617F, LEUCOCYTOSIS AND THROMBOGENIC RISK IN PATIENTS WITH POLYCYTHEMIA VERA AND ESSENTIAL THROMBOCYTHEMIA

Thrombotic events (TE) are the most common, debilitating and fatal complications in Polycythemia Vera (PV) and Essential Thrombocythemia (ET). Approximately 20% of patients have experienced TE at the time of diagnosis. The subsequent cumulative incidence of non-fatal thrombosis is 3.8 incidents/100 patients / year [1, 2]. The risk stratification divides patients by age and a history of thrombosis. There is controversy in the literature about the impact of JAK2 V617F allel burden and changes in peripheral blood counts on the TE frequency. Aim: The aim of this study is to evaluate the influence of JAK2 V617F allel burden and changes in leukocyte count on the development of thrombotic events in patients with PV and ET. Methods: We performed a retrospective analysis of the data of 96 patients with PV and 43 patients with ET diagnosed according to the WHO criteria. JAK2 mutational burden was determined by RealTime-PCR. The statistical analysis was performed with SPSS 19.0 software. Results: In the group of PV patients, thrombotic events were recorded in 46 patients. We did not find a correlation between higher levels of JAK2 V617F allel burden and frequency of TE. Clinically, patients with a higher mutational burden had more pronounced splenomegaly. There was no correlation between leukocytosis at the diagnosis and the number of TE, but there was a significant correlation between leukocytosis and the presence of splenomegaly. In the group of ET patients (43) we established TE in 13 of them, and 54% were carriers of JAK2 V617F. There was no relationship between the frequency of TE and the increased leukocyte count. Unlike PV patients, the presence of JAK2 V617F >= 50% was associated with pronounced leukocytosis in the group with ET patients. Conclusions: The JAK2 V617F allel burden and leukocytosis level are prothrombogenic, but are not a predetermining factor for thrombosis. The current risk stratification criteria for PV and ET, although common, reflect the complexity of thrombotic complications. Clotting mechanisms are different not only in both diseases but also in different parts of the vascular system. More studies are needed involving the functional state of the vascular system to help differentiate individual arterial and venous thrombotic index for each disease.