This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Pathology
[{'content': 'The earliest sign of iron deficiency anaemia- \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: The first stage in the development of iron deficiency anaemia is the depletion of storage iron. The iron reserves are lost without compromise of iron supply for erythropoesis.Therefore the earliest sign is decreased serum ferritin level indicating poor tissue iron stores. Reference : Harsh Mohan textbook of pathology, 7th edition.Pg no.275,276 Ref Robbins 9/e pg 412', 'role': 'assistant'}]