This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'Which of the following is the most sensitive and specific test for diagnosis of iron deficiency? \nSelect and explain. \nA. Serum iron levels, B. Serum ferritin levels, C. Serum transferrin receptor population, D. Transferrin saturation', 'role': 'user'}, {'content': "Answer: B \nExplanation: The serum ferritin level correlates with total body iron stores so it is the most sensitive and specific laboratory test to estimate iron stores in the body. An average normal level of ferritin in an adult male is 100 g/L, while in adult females it is 30 g/L. As the iron stores are depleted, the serum ferritin falls to diagnostic of absent body iron stores. Ref: Harrison's Internal Medicine, 18th Edition, Chapter 103", 'role': 'assistant'}]