This patient should continue anticoagulation therapy indefinitely. Because his venous thromboembolism (VTE) was unprovoked, he is at relatively high risk for recurrence if he stops anticoagulation. Based on his history, stable INR values, absence of comorbidities, and age, his bleeding risk is low. He also does not have a strong preference to discontinue anticoagulation. The decision to treat him for an extended period of time is consistent with the American College of Chest Physicians guidelines, which suggest extended anticoagulant therapy in patients with unprovoked proximal leg deep venous thrombosis (DVT) or pulmonary embolism who have low or moderate bleeding risk. Re-evaluation of this indication based on periodic risk/benefit assessments, new clinical study data, and new anticoagulation drug availability is appropriate.

Short-term anticoagulant therapy (3 months) is suggested for patients with VTE associated with a major transient risk factor, such as major surgery, trauma, or immobility; patients with unprovoked distal leg DVT; and patients with unprovoked proximal leg DVT who are at high risk for bleeding. Therefore, 3 months of therapy, or extending treatment to 6 months, would not be optimal treatment for this patient with an unprovoked proximal DVT.

Because identification of an inherited thrombophilia often does not change treatment decisions in a patient with VTE (does not reliably predict risk of recurrence or influence duration of recommended anticoagulation), evidence-based guidelines recommend against routine thrombophilia testing. In this patient with an unprovoked proximal DVT, the recommendation for long-term anticoagulation would not be altered by the results of such testing, thus, it would not be helpful. Testing may be indicated, however, in patients with VTE at intermediate risk for recurrence by traditional predictors in whom finding a strong thrombophilic risk might alter therapeutic decisions.