Evaluation of the Duration of Therapy for Thrombosis in Children

Inclusion Criteria:

   1. Children (birth to <21 years of age) with radiologically-confirmed acute deep 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. Malignancy that, in the opinion of the treating oncologist, is not in remission (note:
   remission may exist on or off anti-neoplastic therapy)

   3. Systemic lupus erythematosus

   4. Pulmonary embolism that is not accompanied by DVT or is more proximal than segmental
   branches of the pulmonary artery

   5. Use of, or intent to use, thrombolytic therapy

   6. Chronic anticoagulant at prophylactic dosing is being or will be administered beyond 6
   months post VTE diagnosis

   7. Moderate/severe anticoagulant deficiency (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.