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    Poster Networking

    Platelet Disorders, von Willebrand Disease and Thrombotic Microangiopathies

    Poster Networking Session

    PB0852 - Abnormal von Willebrand factor test in patients with extreme thrombocytosis

    Monday, June 26, 2023
    18:30 – 19:30 ET
    Room: Exhibition

      Presenting Author(s)

    • Jian Chen, MD, PhD

      Director, Clinical Coagulation Laboratory
      Houston Methodist Hospital
      Houston, Texas, United States

      • Co-Author(s)

    • ML

      Michael Losos

      Director, Clinical coagulation laboratory
      Ohio State University Wexner Medical Center
      Columbus, Ohio, United States

    Background: Patients with extreme thrombocytosis often have abnormal von Willebrand factors (VWF), a condition that is sometimes referred to as acquired von Willebrand syndrome (aVWS). However, there is no consensus on the definition/diagnostic criteria of aVWS. Therefore, the diagnosis of aVWS has not been useful in assessing patient’s bleeding risk or making therapeutic decisions.

    Aims: Investigate VWF changes in patients with thrombocytosis and correlate with bleeding history.

    Methods: In this retrospective study, we reviewed more than 1400 patients with a platelet count greater than 750K/uL and 150 cases of VWF studies that were performed in our laboratory from 2020 to 2022. Among them, 29 patients with thrombocytosis were evaluated for VWD and all of them had platelet count greater than 1000K/uL. Twenty-three patients had VWF antigen (VWFAG), immunofunction assay (VWFI), collagen binding (VWFCB), and multimer studies and the other 6 had no multimer studies.

    Results: Essential thrombocytosis was the most common cause of thrombocytosis (72%), followed by a reactive etiology (24%). 87% of these 29 patients had a decreased high molecular weight multimer (HMWM), 54% had decreased VWFI/VWFAG ratio, and 30% had decreased VWFCB/VWFAG. All of them had normal VWFAG. There was a strong correlation between HMWM and VWFI/VWFAG ratio (p < 0.001, R=0.711). Four patients had a history of bleeding or easy bruising, however an alternative cause was deemed the etiology by their treating hematologists. Additionally, these 4 patients all had a normal VWFAG (range 111-150%), and 2 patients had a decreased VWFI/VWFAG but only 1 had slightly decreased VWFCB/VWFAG of 0.56 (normal range >0.6).

    Conclusion(s): Decreased HMWM is a very common abnormality in patients with extreme thrombocytosis. More than half of these patients also had decreased VWFI/VWFAG. None of these patients had abnormally low VWFAG. Clinical history did not support abnormal VWF as a plausible etiology in patients with bleeding events.