Which test is crucial in evaluating the effectiveness of heparin therapy?

The Partial Thromboplastin Time (PTT) test is crucial in evaluating the effectiveness of heparin therapy because it specifically measures the time it takes for blood to clot in the presence of intrinsic pathways of coagulation, which are affected by heparin. Heparin is an anticoagulant that primarily influences the intrinsic and common coagulation pathways, prolonging the clotting time. By monitoring PTT, healthcare providers can assess whether the heparin dosing is adequate to achieve the desired level of anticoagulation without increasing the risk of bleeding. This makes PTT the preferred test for managing patients on heparin therapy, allowing for timely adjustments in medication if needed.

Other tests such as Prothrombin Time (PT) are more relevant for monitoring warfarin therapy because they evaluate the extrinsic pathway affected by vitamin K. Platelet counts and Complete Blood Counts (CBC) provide important information about overall blood health but do not specifically indicate the anticoagulation status related to heparin. Hence, PTT is the primary test that directly correlates with the therapeutic effect of heparin.