What lab test is commonly used to monitor unfractionated heparin therapy?

What lab test is commonly used to monitor unfractionated heparin therapy?

• A. Activated partial thromboplastin time (aPTT)
• B. Prothrombin time (PT/INR)
• C. Complete blood count
• D. D-dimer

Answer: (A)

Monitoring unfractionated heparin relies on a test that reflects its effect on the clotting cascade, specifically the intrinsic and common pathways. Heparin works by enhancing antithrombin III, which inhibits thrombin and factor Xa. The activated partial thromboplastin time measures how long it takes for plasma to clot after intrinsic pathway activation; as heparin levels rise, this time lengthens. Clinically, targets are set to achieve effective anticoagulation without excessive bleeding, often expressed as a range relative to the baseline. Because of this direct relationship between heparin activity and the aPTT, it is the standard test used to titrate unfractionated heparin therapy. In contrast, prothrombin time/INR monitors the extrinsic pathway and is used for warfarin; a complete blood count assesses cells and platelets rather than anticoagulant effect; D-dimer reflects clot breakdown and is not used to gauge heparin levels.

Monitoring unfractionated heparin relies on a test that reflects its effect on the clotting cascade, specifically the intrinsic and common pathways. Heparin works by enhancing antithrombin III, which inhibits thrombin and factor Xa. The activated partial thromboplastin time measures how long it takes for plasma to clot after intrinsic pathway activation; as heparin levels rise, this time lengthens. Clinically, targets are set to achieve effective anticoagulation without excessive bleeding, often expressed as a range relative to the baseline. Because of this direct relationship between heparin activity and the aPTT, it is the standard test used to titrate unfractionated heparin therapy. In contrast, prothrombin time/INR monitors the extrinsic pathway and is used for warfarin; a complete blood count assesses cells and platelets rather than anticoagulant effect; D-dimer reflects clot breakdown and is not used to gauge heparin levels.