INR Targets in Venous Thromboembolism
International Normalized Ratio (INR) targets should only be used for the monitoring of warfarin. Warfarin is less commonly used for venous thromboembolism due to the advent of direct-acting oral anticoagulants (DOACs), which typically require no monitoring. Warfarin also requires bridging with low molecular weight heparin (LMWH) due to the delayed effects of getting to a therapeutic INR within the first few days of initiation. [1] In cases where cost is a significant factor or DOACs are unavailable, the use of warfarin may be preferred.
The guidelines below are based on the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines for Antithrombotic Therapy and Prevention of Thrombosis (ninth edition, 2012). [2]
Acute pulmonary embolism (PE) [3, 4]
International normalized ratio (INR) target (range)
-
Standard: 2.5 (2.0-3.0)
-
Unprovoked, infrequent INR checks: 1.5-1.9 after 3 months of standard therapy
Duration of therapy
-
Transient, reversible risk factor: 3 months
-
First episode, unprovoked
Low/moderate bleeding risk: Extended therapy
High bleeding risk: 3 months
-
Recurrent, unprovoked
Low/moderate bleeding risk: extended therapy
High bleeding risk: 3 months
-
Cancer: Extended therapy, if recurrent venous thromboembolism (VTE) consider switching to LMWH [5]
Acute deep venous thrombosis (DVT) of the lower extremity
INR target (range)
-
Standard: 2.5 (2.0-3.0)
Duration of therapy
-
Transient, reversible risk factor: 3 months
-
First episode, unprovoked, proximal
Low/moderate bleeding risk: Extended therapy
High bleeding risk: 3 months
-
First episode, unprovoked, distal: 3 months (guidelines suggest serial imaging for 2 weeks rather than early anticoagulation for patients with isolated distal lower-extremity DVT who do not have severe symptoms or risk factors for extension)
-
Recurrent, unprovoked
Low/moderate bleeding risk: Extended therapy
High bleeding risk: 3 months
-
Cancer: Extended therapy if recurrent VTE consider LMWH [5]
Acute DVT of the upper extremity
INR target (range): 2.5 (2.0-3.0) [6]
Duration of therapy
-
Axillary or more proximal: 3 months or more
-
Distal: 3 months
-
Central venous catheter (CVC) related: Until catheter is removed, or a minimum of 3 months
Acute DVT in children
INR target (range) [7]
-
Standard: 2.5 (2.0-3.0)
-
CVC related: 1.5-1.9 after 3 months of standard therapy
Duration of therapy
-
Idiopathic, first episode: 6-12 months
-
Idiopathic, recurrent: Lifelong therapy
-
Reversible risk factor: Until risk factor has resolved, or a minimum of 3 months
-
Cancer, thrombophilia: Until risk factor has resolved, or a minimum of 3 months
-
CVC related: Until CVC is removed, or a minimum of 3 months