This is a multi-center, retrospective, study to determine if therapeutic dose anticoagulation (High dose group) improves inpatient mortality in severely ill patients with COVID-19 compared to prophylactic dose anticoagulation (Low dose group). The study involved 704 individuals who were admitted to Beaumont Health System (BHS) from March 10th to April 15th, 2020.

Inclusion Criteria:

• Age >18 years old
• positive reverse transcription-polymerase chain reaction (rRT-PCR) test for the qualitative detection of nucleic acid from SARS-CoV-2 in upper and lower respiratory specimens.
• Intensive care unit (ICU) patient or Step-down unit (SDU) patient on invasive mechanical ventilation, BiPAP, 100% non-rebreather mask, or high flow oxygen or supplemental oxygen of at least 4 liters per minute nasal cannula.
• peak d-dimer levels exceeding 1,000 mcg/mL at any time during admission.

Exclusion Criteria:

• Hospital length of stay less than 5 days.
• Hemorrhage before ICU/SDU admission.
• Treatment with an anticoagulant other than low molecular weight heparin or unfractionated heparin.
• Constant treatment with the same dose of anticoagulant for less than 5 days.

Adult patients who were admitted to Beaumont Health System (Michigan, USA) ICU/SDU in the period of March 10th to April 15th, 2020.