American Medical Certification Association (AMCA) Phlebotomy Practice Exam

What medication is commonly associated with the PT/INR test?

1. Aspirin

2. Warfarin

3. Heparin

4. Clopidogrel

The correct answer is: Warfarin

The PT/INR test is primarily designed to monitor patients who are on anticoagulant therapy, particularly those taking warfarin. Warfarin is a vitamin K antagonist that slows down the body's ability to form clots, thereby effectively preventing thromboembolic disorders. The PT (Prothrombin Time) and its derived measure, INR (International Normalized Ratio), allow healthcare providers to assess the coagulation status of patients on this medication, helping to ensure that they remain within a therapeutic range to prevent both clotting and excessive bleeding. In contrast, while aspirin, heparin, and clopidogrel do have effects on blood clotting, they are not consistently monitored through the PT/INR test. Aspirin is an antiplatelet agent rather than an anticoagulant and is typically not monitored using PT/INR. Heparin is monitored using aPTT (activated partial thromboplastin time) when given as a continuous infusion. Clopidogrel, also an antiplatelet medication, is not associated with PT/INR monitoring either. Hence, warfarin's specific influence on the coagulation pathway makes it the medication most closely linked with the PT/INR test.