Ferritin
Deficiency

In the setting of anemia, low serum ferritin is the most specific lab finding for iron-deficiency anemia. However it is less sensitive, since its levels are increased in the blood by infection or any type of chronic inflammation, and these conditions may convert what would otherwise be a low level of ferritin from lack of iron, into a value in the normal range. For this reason, low ferritin levels carry more information than those in the normal range. A falsely low blood ferritin (equivalent to a false positive test) is very uncommon, but can result from a hook effect of the measuring tools in extreme cases.
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