ACCS Practice Exam 2025 – Complete Test Preparation Guide

The activated partial thromboplastin time (aPTT) is the coagulation parameter that is commonly monitored in patients receiving heparin therapy. Heparin, which is an anticoagulant, acts by enhancing the effect of antithrombin III, leading to the inhibition of factors involved in the coagulation cascade, particularly factor Xa and thrombin. The aPTT specifically measures the intrinsic and common pathways of coagulation, making it the most relevant test for evaluating the effectiveness and safety of heparin therapy.

Regular monitoring of aPTT allows healthcare providers to adjust the dosage of heparin to achieve the desired anticoagulation effect while minimizing the risk of bleeding complications. While other tests like prothrombin time (PT) and international normalized ratio (INR) are useful for monitoring vitamin K antagonists like warfarin, they are not relevant for heparin, which operates through a different mechanism. Thrombin time is primarily used to assess the conversion of fibrinogen to fibrin and is not specific to heparin therapy.

In conclusion, the aPTT is the key test for monitoring anticoagulation in patients on heparin, providing crucial information to guide therapy adjustments.