Final answer:
The nurse should identify that an INR of 2.0 indicates the medication is effective in preventing blood clots.
Step-by-step explanation:
The nurse should identify that an INR of 2.0 indicates the medication is effective. The INR measures the speed of coagulation, with a higher value indicating a longer time taken for blood to clot. Warfarin is an anticoagulant medication used to prevent blood clots, so an INR of 2.0 suggests that the medication is effectively preventing excessive blood clotting in the client.