The goal of this single-center, non-controlled, non-randomized exploratory clinical trial is to evaluate the interpretability of viscoelastic tests (Quantra® and ROTEM® type) in relation to platelet levels measured in standard biology in patients with haematological malignancies, hospitalized in day hospitals or full hematology wards, presenting thrombocytopenia strictly below 50 G/L.

Participants will undergo an additional blood sample to standard care. The total volume of blood drawn will be 12.1 mL. The following analyses will be performed: Quantra®, Rotem®, blood count, platelets, immature platelet count, plasma prothrombin time, activated partial thromboplastin time, International Normalized Ratio, fibrinogen.

Inclusion Criteria:

• Patient age > 18 years old ;
• Patients who have been informed of the study and have freely given their informed consent to participate in the study;
• Patients with hematologic malignancies, treated or untreated, at any stage of treatment;
• Patient with thrombocytopenia strictly below 50 G/L on a blood sample taken less than 72 hours ago;
• Patient hospitalized in day hospitalization or in full hematology hospitalization;
• Patient covered by a French social security scheme.

Exclusion Criteria:

• Patients treated with antiplatelet agents or anticoagulants in preventive or curative doses;
• Patient with a history of thrombopathy;
• Patient with a history of haemostasis pathology at risk of haemorrhage or thrombosis;
• Pregnant or breast-feeding patients;
• Patients under guardianship;
• Patients who do not understand French;
• Patients under court protection.