Evaluation of the Duration of Therapy for Thrombosis in Children (Kids-DOTT)

Inclusion Criteria:

1. Children (birth to <21 years of age) with radiologically-confirmed acute venous thrombosis in the past 30 days
2. In the opinion of the investigator, the venous thrombosis was a provoked (i.e., non-spontaneous) event (e.g.: hospitalization; Central venous catheterization; infection; dehydration; surgery; trauma; immobility; use of estrogen-containing oral contraceptive pills; flare of autoimmune/rheumatologic condition).

Exclusion Criteria:

1. prior episode of VTE;
2. presence or history of cancer;
3. systemic lupus erythematosus
4. known pulmonary embolism (PE), except when limited to peripheral cavitary lesions representing septic emboli; (N.B. imaging for PE should only have been based upon clinical signs/symptoms, and is not a study procedure or requirement)
5. Use of, or intent to use, thrombolytic therapy
6. Patients with congenital cardiac disease involving a single or hypoplastic ventricle or otherwise requiring an intracardiac shunt

7. Moderate/severe anticoagulant deficiency as defined by any one of the following:

   1. protein C <20 IU/dL if patient is ≥3 months of age, or protein C below lower limit of detection if patient is <3 months of age;
   2. antithrombin <30 IU/dL if patient is ≥3 months of age, or antithrombin below lower limit of detection if patient is <3 months of age;
   3. protein S (free antigen or activity) <20 IU/dL.