PB1186 - Myeloproliferative neoplasms with thrombocytosis and acquired von Willebrand disease: a single centre experience.

Background: Local guidelines at Oxford University Hospitals recommend screening patients with myeloproliferative neoplasms (MPN) for acquired von Willebrand disease (aVWD) if the platelet count is >1000x10^9/L or if bleeding concerns.

Aims: We undertook a retrospective review to assess impact of this guideline.

Methods: The local laboratory identified 41 patients with MPN who had von Willebrand factor (VWF) testing and thrombocytosis (>750x10^9/L) between August 2020 and September 2023. Electronic Patient Records were reviewed for details related to MPN and aVWD (audit approval number 8940).

Results: Primary reasons for undertaking the initial VWD test were: routine screening with thrombocytosis (78.0%), bleeding symptoms (9.8%), pre-invasive procedures (12.2%); 7 patients had recent thrombotic event resulting in referral and new diagnosis MPN. Laboratory testing demonstrated definite aVWD in 29 patients (70.7%): all patients (100%) had VWF activity:antigen ratio < 0.7, and 13 patients (44.8%) had VWF activity < 50%. Four patients (12.1%) had possible aVWD based on borderline laboratory results. Of the 29 patients with definite aVWD, it was recognised by the clinical team in 19 (65.5%) resulting in change in management: 6 had bone marrow biopsy delayed, 2 had antiplatelet primary prophylaxis delayed, and 11 had ‘additional caution’ though no change in antiplatelets/anticoagulants. Of the 4 patients tested for bleeding, only 2 had aVWD; 3 other patients had minor bleeds documented following aVWD diagnosis. No major bleeding events were documented in patients with unrecognised aVWD. Only 6 patients had repeat VWF testing when platelets were < 600x10^9/L; of these, 4 showed resolution of aVWD (mean platelet count 493.5 x10^9/L, range 416-579), and 2 showed persistent activity:antigen discrepancy (platelet counts 528 and 542x10^9/L).

Conclusion(s): aVWD due to activity:antigen discrepancy was not always recognised by the clinical team; but recognition resulted in changes in management. This demonstrates the need to review processes, including for recognition of aVWD and checking for resolution.