Please select the eligibility criteria that correspond to the clinical trial below.
Title: Aspirin After Six Months or One Year of Oral Anticoagulants for the Prevention of Recurrent Venous Thromboembolism in Patients With Idiopathic Venous Thromboembolism. The WARFASA Study.
Brief Summary: To determine whether aspirin is more effective than placebo for the prevention of recurrent symptomatic venous thromboembolism when given for at least two years after the initial 6-12 month of oral anticoagulant therapy in patients with idiopathic venous thromboembolism


Options:
A: Inclusion Criteria:

* aged \>= 18 years
* needing admission to a medical hospital division or to an ICU
* with a confirmed infection for COVID-19

Exclusion Criteria:

* aged \< 18 years
B: Inclusion Criteria:

* first episode of symptomatic, objectively confirmed idiopathic proximal deep vein thrombosis and/or pulmonary embolism;
* initial treatment with unfractionated heparin or low-molecular-weight heparin (or effective alternative) followed by a vitamin K antagonist (target INR 2.0-3.0). All patients will receive 6 or 12 months of oral anticoagulant treatment. Patients initially treated with thrombolytic therapy who received warfarin therapy are eligible for inclusion.

Exclusion Criteria:

* permanent risk factors for venous thromboembolism: patients known to have antiphospholipid antibodies or lupus anticoagulant (based on local laboratory criteria) or to have homozygous factor V Leiden or homozygous prothrombin G21210A or heterozygous factor V Leiden plus heterozygous prothrombin G21210A or antithrombin III deficiency; patients with active malignancy
* temporary risk factors for venous thromboembolism
* any recurrence of venous thromboembolism or bleeding episode during the established 6-month period of oral anticoagulant treatment
* allergy or intolerance of aspirin
* clear indication for aspirin or other anti-platelet therapy (e.g. clopidogrel, ticlopidine)
* clear indication for long-term anticoagulant therapy (e.g. recurrent idiopathic venous thromboembolism, prosthetic heart valve)
* treatment with non-selective COX-1/2 non-steroidal anti-inflammatory drugs
* life expectancy less than 6 months
* active bleeding or at high risk of bleeding (gastrointestinal bleeding within the past 12 months; endoscopic diagnosis of peptic ulcer disease or ulcerative esophagitis within the past 6 months unless there is documented endoscopic evidence of healing; intracranial bleeding within the past year; known bleeding diathesis)
* anticipated non-adherence to study medications
* inability to attend follow up because of geographic inaccessibility
* failure to provide informed consent
C: Inclusion Criteria:

* Laboratory confirmed SARS-CoV-2 infection
* Age ≥18 years
* Requires hospital admission for further clinical management
* Modified ISTH Overt DIC score ≥ 3

Exclusion Criteria:

* Indication for full therapeutic-dose anticoagulation
* Acute venous thromboembolism (deep vein thrombosis or pulmonary embolism) within prior 3 months
* Acute cardiovascular event within prior 3 months
* Acute stroke (ischemic or hemorrhagic) within prior 3 months
* Active major bleeding
* Severe thrombocytopenia (\<25,000/mm3)
* Increased risk of bleeding, as assessed by the investigator
* Acute or chronic renal insufficiency with Creatinine Clearance \< 30 ml/min calculated by the modified Cockcroft and Gault formula
* Weight \< 40 kg
* Known allergies to ingredients contained in enoxaparin, allergy to heparin products or history of heparin induced thrombocytopenia
D: Inclusion Criteria:

1. Men or women 18 years or older.
2. Body mass index (BMI) of 35kg/m2 or greater.
3. Undergoing laparoscopic bariatric surgery, i.e., laparoscopic sleeve gastrectomy, laparoscopic Roux-en Y gastric bypass or laparoscopic duodenal switch.

Exclusion Criteria:

1. History of previous deep vein thrombosis.
2. History of previous pulmonary emboli.
3. History of documented clotting/coagulation disorder.
4. History of cancer.
5. Weight \< 50 kg or \> 200 kg or unable to fit in MRI scanner.
6. Presence of metallic foreign bodies
7. Recent history of smoking (within the last year).
8. History of venous stasis disease.
9. History of obesity hypoventilation syndrome.
10. Patients who are unable to lay flat for extended periods of time or are claustrophobic.
11. Patients who have a pacemaker, an implanted defibrillator or certain other implanted or electronic or metallic devices (implanted medical or metallic devices, shrapnel, or metal).
12. History of hypersensitivity reaction to anticoagulation products.
13. History of HIT (Heparin Induced Thrombocytopenia.
14. History of Renal Insufficiency (Creatinine Clearance \< 50).
15. Active clinically significant bleeding.
16. Acute bacterial endocarditis.
17. BMI \> 60.
18. Patients with metallic foreign body or implant (unable to have an MRV study).

Answer: B