Management and Outcomes of Anti-thrombotic Medication Use in Thrombocytopenia

Plain-language summary

Background: Antithrombotic therapy in the context of treatment related thrombocytopenia (i.e. low levels of platelets) is not uncommon. Guidelines are based upon a paucity of retrospective data and focus on the scenario of cancer associated venous thrombosis and low molecular weight heparin treatment. Even less is known regarding direct oral anticoagulants, antiplatelet therapy, or anticoagulation prescribed for other indications. Aims: The study aims are to evaluate how physicians manage anticoagulant and antiplatelet medication in patients with hematological malignancy and thrombocytopenia, and to assess the frequency of bleeding and thrombosis. Additional aims are to assess how management changes affect drug activity and blood clotting (coagulation), and to evaluate the use of platelet transfusions. Design: The investigators plan a multinational prospective registry of patients admitted to the inpatient hematology department or outpatient clinic at one of the study centers. Patients with hematological malignancies, platelets below 50 X 109/L, and anticoagulant and/or antiplatelet medication will be studied. Patients will be enrolled when the combination of antiplatelet/anticoagulant medication and thrombocytopenia is first detected. Patients will be followed until 30 days after the baseline study visit (which occurs 30 days after enrollment or when platelets \< 50\*109/L, whichever come first) or death. Patients will be indexed at the time of baseline visit. Patients will be excluded from study analysis if one of the following events occurs before study index: Withdrawal of consent, death, clinically-relevant non-major bleeding or the composite primary outcome. Risk factors for bleeding and thrombosis will be recorded at baseline. Parameters from routine blood tests will be recorded throughout the study. During the study major bleeding events and thrombosis will be recorded. Investigational blood tests assessing coagulation and drug activity will be drawn at baseline (=study index). Throughout the study all management decisions regarding antithrombotic therapy, including platelet and red blood cell transfusion, will be recorded. This is an observational study and management will be solely at the discretion of the physician. Analysis: The investigators will first look at the frequency of either bleeding or thrombosis according to the type of management strategy and evaluate the platelet threshold at which a given management strategy is employed. At the next stage, in selected subgroups, the optimal management strategy with respect to bleeding/thrombotic risk, will be determined.

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