Anticoagulation Monitoring

Optimal management of anticoagulant therapy requires an understanding of the laboratory tests often employed to guide therapy. The activated partial thromboplastin time (aPTT) can detect abnormalities in the intrinsic and common clotting pathways. Despite numerous limitations in the aPTT test, it remains the gold standard for monitoring unfractionated heparin and direct thrombin inhibitor therapy. The aPTT can be performed in the central laboratory or at the bedside (point of care [POC] testing). The activated clotting time (ACT) is a POC test that is routinely employed to monitor high-dose heparin during invasive and surgical procedures. The ACT therapeutic range will depend on the specific procedure or surgery being performed. Heparin levels are becoming more routinely available and are used to establish the aPTT therapeutic range for heparin therapy as well as for direct monitoring of heparin and low-molecular-weight heparin therapy. The international normalized ratio (INR) is the gold standard for monitoring warfarin patients. The target INR depends on the indication for anticoagulation. POC monitoring for warfarin is becoming increasingly used. Clinicians should have a thorough understanding of the benefits as well as the limitations of warfarin POC monitoring.