<prompt> Most sensitive and specific test for diagnosis of iron deficiency is:Serum iron levelSerum ferritin levelsSerum transferrin receptor populationsTransferrin saturation  <response>: b. Serum ferritin levelsRef: Nelsons 20e p 2323-2325, Ghai 8e p 334-335Low serum ferritin level invariably indicates iron deficiency and hence it is the most specific and sensitive test for iron deficiency anemia. 