Correlation between diagnostic 59Fe2+-absorption and serum ferritin concentration in man.

A high correlation coefficient r = -0.832 (P r +/- 0 less than 0.0001) was estimated in man for the inverse relationship between the diagnostic 59Fe2+-absorption and the serum ferritin concentration which is very close to the correlation r = -0.88 as described for the relationship between the diagnostic 59Fe2+-absorption and the diffuse cytoplasmic storage iron in the bone marrow macrophages. The increase of the diagnostic 59Fe2+-absorption seems to be an earlier and more sensitive indicator of depleted iron stores whereas the serum ferritin decreases somewhat later during the development of iron deficiency.