A nurse is reporting a client's laboratory tests to the provider to obtain a prescription for the client's daily warfarin. Which of the following laboratory tests should the nurse plan to report to obtain the prescription for the warfarin?

A. Platelet count. While important for evaluating bleeding risk, platelet count is not directly used to adjust or determine daily warfarin dosing. Warfarin affects the coagulation cascade, not platelet function. B. aPTT. The activated partial thromboplastin time (aPTT) is used to monitor heparin therapy, not warfarin. It assesses the intrinsic pathway of coagulation and is not sensitive to warfarin’s effects on the clotting factors. C. Fibrinogen level. Fibrinogen is involved in clot formation, but its measurement is not part of routine warfarin management. It is more relevant in evaluating bleeding disorders or disseminated intravascular coagulation (DIC). D. INR. The international normalized ratio (INR) is the primary lab value used to monitor the effectiveness and safety of warfarin therapy. It helps guide daily dosing by reflecting how long it takes blood to clot, with therapeutic ranges typically between 2.0 and 3.0 for most conditions.