Background: von Willebrand disease (VWD) is a common inherited bleeding disorder. Significant variability exists in management options offered to patients.Objective: These evidence-based guidelines from the American Society of Hematology (ASH), the International Society on Thrombosis and Haemostasis (ISTH), the National Hemophilia Foundation (NHF), and the World Federation of Hemophilia (WFH) are intended to support patients, clinicians, and health care professionals in their decisions about management of VWD.Methods: ASH, ISTH, NHF, and WFH formed a multidisciplinary guideline panel. Three patient representatives were included. The panel was balanced to minimize potential bias from conflicts of interest. The University of Kansas Outcomes and Implementation Research Unit and the McMaster Grading of Recommendations Assessment, Development and Evaluation (GRADE) Centre supported the guideline development process, including performing and updating systematic evidence reviews (through November 2019). The panel prioritized clinical questions and outcomes according to their importance to clinicians and patients. The panel used the GRADE approach, including GRADE Evidence-to-Decision frameworks, to assess evidence and make recommendations, which were subject to public comment.Results: The panel agreed on 12 recommendations and outlined future research priorities.Conclusions: These guidelines make key recommendations regarding prophylaxis for frequent recurrent bleeding, desmopressin trials to determine therapy, use of antiplatelet agents and anticoagulant therapy, target VWF and factor VIII activity levels for major surgery, strategies to reduce bleeding during minor surgery or invasive procedures, management options for heavy menstrual bleeding, management of VWD in the context of neuraxial anesthesia during labor and delivery, and management in the postpartum setting.

Background An increased risk of thrombosis has been reported in primary immune thrombocytopenia (ITP) and with the use of thrombopoietin (TPO) receptor agonists, on the basis of population studies using administrative databases. Objectives To evaluate if the incidence of venous and arterial thrombosis in patients with primary ITP is higher than a clinically significant cut‐off set at of 3% and 6.4%. Patients/Methods We undertook a retrospective multicenter investigation in a large cohort of patients requiring at least one treatment for ITP, enrolled from the major tertiary Italian centers treating ITP. A total of 986 patients were analyzed. Results During a 3888 patient‐year follow‐up, 43 first thrombotic events occurred: 28 arterial and 15 venous, resulting in a cumulative incidence of 3.2% for arterial (95% CI, 2.0–5.0) and 1.4% (95% CI, 0.8–2.5) for venous thrombosis at 5 years. The annualized rates for 100 patient‐years were 1.14 (95% CI, 0.84–1.54), 0.39 (95% CI, 0.23–0.65) and 0.71 (95% CI, 0.49–1.04) for total, venous and arterial thrombosis. Splenectomy, performed in 136 patients (13.7%), increased thrombotic risk (HR = 3.5, 95% CI) compared with non‐splenectomized patients. Age > 60 years, more than two risk factors for thrombosis at diagnosis and steroid use were independently associated with an increased risk of thrombosis. Conclusions In this study, we demonstrate that the 5‐year cumulative incidence of venous and arterial thrombosis in ITP is well below the predefined thresholds. Venous and arterial thromboembolism are not frequent complications in ITP, except in particular settings, such as in splenectomized and elderly patients.

Essential thrombocythemia (ET) is characterized by abnormal megakaryopoiesis and enhanced thrombotic risk. Once-daily (od), low-dose aspirin is the recommended antithrombotic regimen, but accelerated platelet generation may reduce the duration of platelet cyclooxygenase (COX)-1 inhibition. We performed a multicenter, double-blind trial to investigate the efficacy of three aspirin regimens in optimizing platelet COX-1 inhibition while preserving COX-2-dependent vascular thromboresistance. Two-hundred-forty-five patients on chronic od low-dose aspirin were randomized (1:1:1) to receive 100 mg aspirin od, twice-daily, bid), or three-times daily (tid) for 2 weeks. Serum thromboxane B₂ (sTXB₂), a validated biomarker of platelet COX-1 activity, and urinary prostacyclin metabolite (PGIM) excretion were measured at randomization and after 2 weeks, as primary surrogate endpoints of efficacy and safety, respectively. Urinary TX metabolite (TXM) excretion, gastrointestinal tolerance, and ET-related symptoms were also investigated. Evaluable patients assigned to the bid and tid regimens showed substantially reduced inter-individual variability and lower median values of sTXB₂: 19.3[9.7-40], 4 [2.1-6.7], and 2.5[1.4-5.65] ng/ml in the od (n=85), bid (n=79) and tid (n=79) arms, respectively. Urinary PGIM was comparable in the three arms. Urinary TXM was significantly reduced by 35% in both experimental arms. Patients in the tid arm reported a higher abdominal discomfort score. In conclusion, the currently recommended aspirin regimen of 75-100 od for cardiovascular prophylaxis appears largely inadequate in reducing platelet activation in the vast majority of ET patients. The antiplatelet response to low-dose aspirin can be markedly improved by shortening the dosing interval to 12 hours, with no improvement by further reducing it. (EudraCT 2016-002885-30)