This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition and health, Subject name: Social & Preventive Medicine
First indices to change in iron deficiency anemia is - 
Select and explain. 
A. S. Iron, B. Total iron binding capacity, C. S. Ferritin, D. S. Haemoglobin concentration
C: S. Ferritin
Answer: C: S. Ferritin 
Explanation: The single most sensitive tool for evaluating the iron status is by measurement of serum ferritin. Hemoglobin concentration is relatively insensitive. REF. PARK'S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICAL 21ST EDITION. PAGE NO - 623