A nurse is caring for a client who is prescribed warfarin therapy for an artificial heart valve. Which of the following laboratory values should the nurse monitor for a therapeutic effect of warfarin?

A. Hemoglobin levels are not specific indicators for warfarin therapy or its effectiveness. While they may reflect blood loss, they do not directly monitor the therapeutic effect of warfarin. B. Prothrombin time (PT) is directly related to the effectiveness of warfarin. It measures the time it takes for blood to clot and is used to monitor anticoagulant therapy. C. Bleeding time is a general test for clotting, but it is not specific for monitoring warfarin’s anticoagulant effects. PT is the standard for this purpose. D. Activated partial thromboplastin time (aPTT) is used to monitor heparin therapy, not warfarin. Warfarin requires PT monitoring.