Coagulopathy of COVID-19: A Pragmatic Randomized Controlled Trial of Therapeutic Anticoagulation Versus Standard Care

2-arm, parallel, pragmatic, multi-centre, open-label randomized controlled trial to determine the effect of therapeutic anticoagulation, with low molecular weight heparin or unfractionated heparin (high dose nomogram), compared to standard care in hospitalized patients with COVID-19 and an elevated D-dimer on the composite outcome of intensive care unit (ICU) admission, non-invasive positive pressure ventilation, invasive mechanical ventilation or death at 28 days. Eligible participants will be randomized to one of two treatment regimens, receiving either therapeutic anticoagulation or standard care until discharged from hospital, death or day 28. The primary composite outcome of ICU admission, non-invasive positive pressure ventilation, invasive mechanical ventilation, or all-cause death up to 28 days. Key secondary outcomes between study arms up to day 28 include: 1. All-cause death 2. Composite outcome of ICU admission or all-cause death 3. Composite outcome of mechanical ventilation or all-cause death 4. Major bleeding as defined by the ISTH Scientific and Standardization Committee (ISTH-SSC) recommendation 5. Number of participants who received red blood cell transfusion (≥1 unit) 6. Number of participants with transfusion of platelets, frozen plasma, prothrombin complex concentrate, cryoprecipitate and/or fibrinogen concentrate 7. Renal replacement therapy; 8. Number of hospital-free days alive 9. Number of ICU-free days alive 10. Number of ventilator-free days alive 11. Number of organ support-free days alive 12. Number of participants with venous thromboembolism 13. Number of participants with arterial thromboembolism 14. Number of participants with heparin induced thrombocytopenia 15. Changes in D-dimer up to day 3 The treatment arm is therapeutic anticoagulation with low molecular weight heparin (LMWH) or unfractionated heparin (UFH, high dose nomogram). The choice of LMWH versus UFH will be at the clinician's discretion. LMWH options include: Tinzaparin, Enoxaparin, or Dalteparin. UFH will be administered using a weight-based nomogram with titration according to the center-specific protocol. Therapeutic anticoagulation will be administered until discharged from hospital, 28 days or death. If the patient is admitted to the ICU or requiring ventilatory support, we recommend continuation of the allocated treatment as long as the treating physician is in agreement. The standard care arm is the administration of LMWH, UFH or fondaparinux at thromboprophylactic doses in the absence of contraindication. No study specific bloodwork will be ordered aside from a single D-dimer test (if not collected through standard of care) up to and including day 3 after randomization for all participants in both study arms. In those on the active treatment arm who are receiving UFH, the aPTT or UFH anti-Xa will be drawn according to local institutional UFH nomogram protocol guidance. All laboratory results will be collected from standard of care from admission to hospital discharge, death or 28 days, where available. An optional biobanking component will collect blood at baseline and 2 follow up time points. This study will immediately impact the clinical care of patients with severe COVID-19 internationally, whether the findings are positive or negative, as COVID-19 coagulopathy is a highly prevalent complication of severe COVID-19 and may precede the respiratory manifestations that characterize it.