What laboratory test is primarily used to monitor anticoagulant therapy?

The test primarily used to monitor anticoagulant therapy is Prothrombin Time (PT) and its standardized value, the International Normalized Ratio (INR). This test evaluates the extrinsic pathway of coagulation, which is particularly affected by anticoagulants like warfarin. By measuring the time it takes for blood to clot, healthcare providers can assess how well the anticoagulant is working and adjust dosages accordingly to prevent thrombotic complications while avoiding excessive bleeding.

Other tests listed serve different purposes: a complete blood count (CBC) provides information on overall blood health but does not specifically assess coagulation; a platelet count measures the number of platelets, which is crucial in hemostasis but not directly related to monitoring anticoagulation; and glycated hemoglobin (HbA1c) is used to assess long-term glucose control in diabetics and has no relation to anticoagulant therapy. Thus, PT and INR are the gold standards for managing patients on anticoagulation to ensure safe and effective treatment.