Certified Medical Assistant Practice Exam

For a patient on warfarin (Coumadin) therapy, which blood test is most effective for monitoring their response?

1. Complete Blood Count (CBC)

2. Prothrombin Time (PT)

3. Activated Partial Thromboplastin Time (aPTT)

4. Prothromboplastin time (PTT)

The correct answer is: Prothromboplastin time (PTT)

The most effective blood test for monitoring a patient's response to warfarin therapy is the Prothrombin Time (PT). This test measures how long it takes for blood to clot and is specifically affected by warfarin, which works by inhibiting vitamin K-dependent clotting factors. PT results are often expressed as an International Normalized Ratio (INR), which standardizes results for the purpose of monitoring anticoagulation therapy. Maintaining the INR within a therapeutic range is crucial for preventing thromboembolic events while minimizing the risk of bleeding complications. Other tests mentioned, such as the Complete Blood Count (CBC), are not specifically useful for monitoring anticoagulation as they evaluate different aspects of blood health, including red and white blood cell counts and platelets. The Activated Partial Thromboplastin Time (aPTT) is primarily used for monitoring heparin therapy, not warfarin, as it assesses the intrinsic pathway of coagulation. The Prothromboplastin Time (PTT) is an older term that is now largely replaced by aPTT and is similarly not pertinent for warfarin monitoring. Therefore, PT is the appropriate test, making it essential for effective management of patients on warfarin therapy.