What is the International Normalized Ratio (INR) range for patients with Antiphospholipid Syndrome?

From the Guidelines

The target INR range for patients with antiphospholipid syndrome (APS) should be between 2 and 3 to effectively balance the risk of excessive bleeding against the risk of thrombosis. This recommendation is based on the 2021 guideline for the prevention of stroke in patients with stroke and transient ischemic attack from the American Heart Association/American Stroke Association 1. The guideline suggests that in patients with ischemic stroke or TIA with confirmed antiphospholipid syndrome treated with warfarin, a target INR between 2 and 3 is reasonable to reduce the risk of recurrent stroke or TIA.

Some key points to consider in the management of APS include:

• Antiplatelet therapy alone is recommended for patients with isolated antiphospholipid antibody but do not fulfill the criteria for antiphospholipid syndrome 1
• Warfarin is recommended for patients with ischemic stroke or TIA who meet the criteria for the antiphospholipid syndrome to reduce the risk of recurrent stroke or TIA 1
• Rivaroxaban is not recommended for patients with antiphospholipid syndrome with history of thrombosis and triple-positive antiphospholipid antibodies due to excess thrombotic events compared with warfarin 1

It is essential to note that treatment is typically lifelong for patients with thrombotic APS, and regular INR monitoring is crucial to maintain a stable dose. Patients should also maintain consistent vitamin K intake through diet to avoid fluctuations in INR levels. Direct oral anticoagulants (DOACs) are generally not recommended as first-line therapy for APS, particularly for patients with triple-positive antibody status, due to higher thrombotic recurrence rates compared to warfarin.

From the Research

Anti-Phospholipid INR Range

• The standard anticoagulant treatment for thrombotic antiphospholipid syndrome (APS) is life-long warfarin or an alternative vitamin K antagonist 2.
• The international normalized ratio (INR) is used to monitor anticoagulation intensity in APS patients, with a target INR range of 2.0-3.0 for moderate-intensity warfarin 3.
• However, lupus anticoagulant can affect phospholipid-dependent coagulation monitoring tests, including INR, which may not reflect true anticoagulation intensity in APS patients 2, 4.
• In some cases, the INR may be falsely elevated due to the reaction of the antiphospholipid antibody with the thromboplastin used to measure the protime, which can be seen in both venipuncture and point-of-care results 5.
• The optimal INR range for APS patients may vary depending on the individual patient's risk factors and clinical presentation, and accurate assessment of anticoagulation intensity is essential to optimize anticoagulant dosing and minimize the risk of recurrent thrombosis or bleeding 3, 4.

Key Considerations

• APS patients on warfarin require regular INR monitoring to ensure that their anticoagulation intensity is within the target range 2, 4.
• Point-of-care INR testing may not be reliable in APS patients due to the potential for false elevation, and venipuncture INR testing may be preferred 5.
• Alternative anticoagulants, such as low-molecular-weight heparin or unfractionated heparin, may be used in certain situations, such as anticoagulant-refractory APS or during pregnancy 2, 4.
• The management of APS patients on anticoagulant therapy requires careful consideration of the individual patient's risk factors and clinical presentation, as well as regular monitoring of their anticoagulation intensity 3, 4, 6.