This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Iron Deficiency and Megaloblastic Anemia, Subject name: Pathology
[{'content': 'The earliest sign of iron deficiency anemia \nSelect and explain. \nA. Increase in iron binding capacity, B. Decrease in serum ferritin level, C. Decrease in serum iron level, D. All the above', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' decrease in serum ferritin In iron deficiency anaemia the first change is decrease in iron stores.The decrease in iron stores is demonstrated by decreased serum ferritin level.Remember serum ferritin reflects the amount of storage iron in the body*", 'role': 'assistant'}]