TABLE 5

2021 American College of Chest Physicians guidelines on duration of anticoagulation for deep vein thrombosis, based on risk factors for venous thromboembolism

Risk factorsaRecommendation
Major transient risk factors, occurring up to 3 months before the thrombotic event:

  • Surgery with general anesthesia for longer than 30 minutes

  • Confined to bed in hospital (only “bathroom privileges”) for at least 3 days with an acute illness

  • Cesarean delivery

The guidelines recommend against offering extended-phase anticoagulation (strong recommendation, moderate-certainty evidence)
Minor transient risk factors, occurring up to 2 months before the thrombotic event:

  • Surgery with general anesthesia for less than 30 minutes

  • Admission to hospital for less than 3 days with an acute illness

  • Estrogen therapy

  • Pregnancy or puerperium

  • Confined to bed out of hospital for at least 3 days with an acute illness

  • Leg injury associated with reduced mobility for at least 3 days

The guidelines suggest against offering extended-phase anticoagulation (weak recommendation, moderate-certainty evidence)
In patients with venous thromboembolism diagnosed in the absence of a transient provoking factor, offer extended-phase anticoagulation with a DOAC (strong recommendation, moderate-certainty evidence)
Persistent risk factors:

  • Active cancer (untreated, ongoing treatment or no potential curative treatment)

  • Inflammatory bowel disease

  • Antiphospholipid syndrome

In patients with antiphospholipid syndrome, vitamin K antagonists are suggested over DOACs as first-line treatment (weak recommendation with low-certainty evidence); a vitamin K antagonist can be offered for patients who can’t receive or who decline DOACs (weak recommendation, moderate-certainty evidence)
Unprovoked thrombotic event (no transient or persistent risk factor identified)The guidelines recommend offering extended-phase anticoagulation with a DOAC (strong recommendation, moderate-certainty evidence); in patients who can’t receive a DOAC, extended-phase anticoagulation with a vitamin K antagonist is recommended (weak recommendation, moderate-certainty evidence)

  • ↵a Previous venous thromboembolism is not mentioned clearly in the guidelines as affecting the duration of treatment.

  • DOAC = direct oral anticoagulant

  • Based on information in references 1 and 34.