A nurse is reviewing the laboratory results for a client who is taking warfarin following orthopedic surgery. Which of the following results should the nurse report to the provider?

Choice A rationale A prothrombin time (PT) of 15.5 seconds, while slightly above the normal range of 11 to 12.5 seconds, indicates a mild prolongation of clotting time. For a client on warfarin, a slight elevation in PT is often expected as it reflects the anticoagulant effect. This value alone may not necessitate immediate reporting. Choice B rationale An activated partial thromboplastin time (aPTT) of 45 seconds, slightly above the normal range of 30 to 40 seconds, indicates a minor prolongation in the intrinsic and common pathways of coagulation. While relevant for heparin therapy, its direct significance for warfarin's primary monitoring is less critical. Choice C rationale An International Normalized Ratio (INR) of 5.2 is significantly elevated above the therapeutic range for most conditions, which is typically 2.0 to 3.0 for clients on warfarin. An INR of 5.2 indicates a high risk of bleeding complications due to excessive anticoagulation, requiring immediate provider notification. Normal range is 0.8 to 1.1. Choice D rationale A platelet count of 90,000/mcL is below the normal range of 150,000 to 400,000/mcL, indicating thrombocytopenia. While important for hemostasis, warfarin primarily affects clotting factors, not platelet production. However, a low platelet count combined with high INR further increases bleeding risk, necessitating reporting.