Inclusion Criteria  Patients admitted to hospital with COVID-19, PCR+ SARS-CoV-2 infection (from any specimen) administered thromboprophylaxis with tinzaparin in intermediate or therapeutic dose Age ≥ 18 years Signed informed consent  Exclusion Criteria  Patients admitted to ICU with COVID-19, PCR+ SARS-CoV-2 infection (from any specimen) Age < 18 years Pregnancy Current diagnosis or suspicion of pulmonary thromboembolism or deep vein thrombosis Progression to death was imminent and inevitable within 24 hours from the admission, irrespective of the provision of treatments Not signed informed consent