Which laboratory test is used to monitor the effectiveness of heparin therapy?

The Activated Partial Thromboplastin Time (aPTT) test is specifically designed to measure the efficacy of heparin therapy. Heparin acts primarily on the intrinsic pathway of the coagulation cascade, and the aPTT assesses the integrity of this pathway by measuring the time it takes for blood to clot in response to certain reagents. Monitoring aPTT levels allows healthcare providers to ensure that heparin is anticoagulating the patient effectively, thus helping to prevent thrombotic events or excessive bleeding.

In contrast, Prothrombin Time (PT) is primarily used to monitor warfarin therapy, Complete Blood Count (CBC) provides a broad overview of blood components including red and white blood cells and platelets but is not specific for anticoagulation therapy, and Platelet Count measures the number of platelets in the blood but does not assess the clotting pathway affected by heparin. Thus, aPTT is the appropriate test for monitoring the effectiveness of heparin treatment.