A nurse is caring for a client who has been taking epoetin alfa for 3 months. Which of the following laboratory tests should the nurse monitor to determine the effectiveness of the medication?

A. Troponin: Troponin is used to evaluate cardiac injury, not the effectiveness of epoetin alfa. B. Thyroxine (T4): T4 measures thyroid function, unrelated to epoetin alfa. C. Aspartate aminotransferase (AST): AST is a liver enzyme, not used to monitor epoetin alfa therapy. D. Hgb: Epoetin alfa stimulates erythropoiesis to increase hemoglobin levels in clients with anemia, particularly in chronic kidney disease or chemotherapy.