A Real-World Evaluation of the Association between Elevated Blood Counts and Thrombotic Events in Polycythemia Vera (Analysis of Data from the REVEAL Study)

▪ Background: Polycythemia vera (PV) is a myeloproliferative neoplasm characterized by clonal proliferation of hematopoietic progenitor cells leading to elevated peripheral blood counts. Patients with PV have an increased risk of thrombotic events (TEs). Advanced age and a history of TEs are the components of the conventional risk model used to determine thrombosis risk and treatment strategy (Marchioli. J Clin Oncol. 2005;23:2224-32). Although, multiple studies have shown an association between TEs and elevated hematocrit (HCT) levels, the association between TEs and white blood cell (WBC) or platelet (PLT) counts has not been assessed in a consistent manner. The large, real-world, p rospective Obs ervational Study of Patients with Polycythemia Vera in US Clinic al Practices (REVEAL; NCT02252159) followed patients with PV treated in both community and academic practices. This analysis evaluated the association between elevated blood counts and occurrence of TEs in patients with PV using data from the REVEAL study. Methods: Patients were required to have ≥3 lab values (blood counts) in the post-enrollment period and were excluded if they had a post-enrollment TE but did not have a lab value 45%, WBC >11×10 9/L, PLT >400×10 9/L (Barosi G. Blood. 2013;121:4778-81; Barbui T. Blood. 2015;126:560-1). Linear interpolation was used to determine lab values between observed lab values. Alternative thresholds for WBC (