Blood, 1 May 2003, Vol. 101, No. 9, pp. 3341-3341
Chasing iron deficiency
Programs to eliminate iron deficiency have had limited
success because of the lack of epidemiologic methods to identify iron deficiency. Anemia, per se, is a poor indicator for iron deficiency because it is often mild and because in developing countries, the
prevalence of anemia associated with malnutrition and infection may
exceed iron deficiency anemia. In this issue, Cook and colleagues (page
3359) describe a method for measuring body iron that relies on the
ratio of serum transferrin receptor to serum ferritin measurements, translated into body iron stores in milligrams per kilogram of body
weight. This method provides a continuum of values ranging from
normal, to storage iron depletion, and finally to tissue iron
deficiency (anemia). The original method has been validated in
volunteers subjected to quantitative phlebotomy (Skikne et al, Blood.
1990;75:1870-1876).
In the present study the method was applied to a large number of
samples collected in the NHANES III survey, a study of iron supplementation in pregnant women in Jamaica, and a study of iron fortification in anemic Vietnamese women. The results obtained are
remarkable. A single normal distribution of body iron has been obtained
for US men and pregnant Jamaican women. In trials of iron
supplementation and fortification, it was possible to calculate the
absolute amount of iron absorbed over time in individual subjects. This
was achieved using minute volumes of serum suitable for collection by
capillary specimens, a procedure highly suitable for large-scale field
studies. The pitfalls and limitations of the method were carefully
defined. It is unsuitable for subjects with inflammation or
hepatocellular injury because of their effect on serum ferritin.
Moreover, for ethical reasons, the phlebotomy validation cannot be
applied to children and pregnant women, the groups at highest risk of
nutritional iron deficiency. Nevertheless, the paper by Cook et al
represents a major step forward in the development of suitable
methodology for effective interventional programs to address a major
global health problem.
Chaim Hershko
Shaare Zedek Hospital,
Jerusalem
