Anticoagulation Therapy Monitoring

Introduction to Monitoring

The International Society on Thrombosis and Haemostasis (ISTH) recommends measuring baseline PT with local thromboplastin before starting vitamin K antagonists (VKA) in patients with lupus anticoagulant (LA) 1
For patients with LA, the INR can generally be used for monitoring warfarin therapy, while chromogenic anti-factor Xa assays should be used for heparin monitoring when required 1

If baseline PT is within reference range, the local thromboplastin can be safely used to monitor LA-positive patients on warfarin 1
If baseline PT is prolonged, alternative LA-insensitive thromboplastins should be used 1
Most commercial thromboplastins can be safely used to monitor LA-positive patients on warfarin, provided that an instrument-specific ISI has been determined according to WHO recommendations 1
Point-of-care INR devices should be used with caution in LA patients as results may be unreliable 1

For patients receiving heparin requiring monitoring, chromogenic anti-factor Xa assays (heparin assays) should be used 1
The activated partial thromboplastin time (APTT) is typically prolonged in LA patients, making it unsuitable for heparin monitoring 1

Chromogenic factor X (CFX) assay can be used when INR appears falsely elevated, as it is not affected by LA presence and is more precise and less costly than factor II assays 1
Factor II activity assays are another option, though they may not always agree with factor X levels in LA patients 1
The American College of Cardiology and the International Society on Thrombosis and Haemostasis recommend checking baseline PT before starting vitamin K antagonists and using LA-insensitive thromboplastins for monitoring if baseline PT is prolonged 1
Recombinant relipidated tissue factor-based thromboplastins should be avoided unless they've been specifically tested for LA sensitivity 1
Consider direct oral anticoagulants (DOACs) if stable monitoring cannot be achieved and appropriate for the patient's indication, however, caution is advised due to limited clinical trial data in LA-positive patients 1