<prompt> First indices to change in iron deficiency anemia is -S. IronTotal iron binding capacityS. FerritinS. Haemoglobin concentration  <response>: The single most sensitive tool for evaluating the iron status is by measurement of serum ferritin. Hemoglobin concentration is relatively insensitive. REF. PARKS TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICAL 21ST EDITION. PAGE NO - 623 