You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Most sensitive and specific test for diagnosis of iron deficiency is: and explain in detail?
b. Serum ferritin levels(Ref: Nelson's 20/e p 2323-2325, Ghai 8/e p 334-335)Low serum ferritin level invariably indicates iron deficiency and hence it is the most specific and sensitive test for iron deficiency anemia.