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
Response to iron deficiency anemia is denoted by 
Select and explain. 
A. Restoration of enzymes, B. Reticulocytosis, C. Increase in iron binding capacity, D. Increase in hemoglobin
B: Reticulocytosis
Answer: B: Reticulocytosis 
Explanation: The indicator for a response to iron therapy is reticulocytosis. The response to iron therapy varies, depending on the erythropoietin stimulus and the rate of absorption. Typically, the reticulocyte count should begin to increase within 4-7 days after initiation of therapy and peak at 1-1 1/2 weeks. Harrison 19e 629; ref Robbins 9/e pg 421