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. Fibrinogen level: This test measures a clotting factor important for hemostasis, but it is not routinely used to monitor warfarin therapy. Fibrinogen levels are more relevant in evaluating bleeding disorders or liver function. B. INR: The International Normalized Ratio is the standard test used to monitor warfarin effectiveness. It helps determine the appropriate dosing needed to maintain therapeutic anticoagulation and reduce the risk of bleeding or thromboembolism. C. APTT: Activated partial thromboplastin time is used to monitor heparin therapy, not warfarin. It evaluates the intrinsic pathway of coagulation and is not a reliable indicator of warfarin activity. D. Platelet count: While important in assessing bleeding risk, platelet count does not provide information on the anticoagulant effect of warfarin. It is not used to guide warfarin dosing decisions.