Final answer:
The priority assessment by the nurse when a physician has prescribed epoetin alfa (Epogen) for the client is to monitor the client's hemoglobin and hematocrit levels.
Step-by-step explanation:
The priority assessment by the nurse when a physician has prescribed epoetin alfa (Epogen) for the client is to monitor the client's hemoglobin and hematocrit levels. Epoetin alfa is a medication that stimulates the production of red blood cells in the bone marrow. By monitoring the client's hemoglobin and hematocrit levels, the nurse can determine the effectiveness of the medication in increasing red blood cell production and improving the client's condition.