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: Social & Preventive Medicine
[{'content': 'Which of the following is the single MOST sensitive status for evaluating body iron status? \nSelect and explain. \nA. Serum transferrin saturation, B. Serum ferritin, C. Serum iron, D. Hemoglobin concentration', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The single most sensitive indicator of body iron status is serum ferritin level. Levels of < 10 mcg/ L indicates iron deficiency. Ref: Park 21st edition, page 576.', 'role': 'assistant'}]