2 - Clinical Measurements of Iron Absorption

Abstract

SUMMARY There have been several important advances in methods to assess iron assimilation in man. The optimal technique for determining the retention of administered radioiron depends on the objective of the study. When comparing the availability of different forms of iron, multiple tests in the same subject are made possible by dual radioiron tags and measurement of incorporated red cell activity. In clinical stud ies a whole-body counter employing shadow shielding and longitudinal scan geometry offers the most convenient and accurate approach. A vexing problem is the wide varia bility in iron absorption measurements. This is due to physiological variability or day-to-day variations within the same subject and biological varia bility between individuals which in turn reflect differences in iron status. The former can be reduced by multiple dose administration while the latter can be eliminated by relating absorption to an independent measure of iron stores such as the serum ferritin level or absorption from a reference dose of inorganic radioiron. The most important advance in recent years is the technique of double extrinsic tagging of haem and non-haem iron to measure absorption from a complete meal or a normal diet. This method will provide important quantitative data of the role of food iron assimilat ion in the pathogenesis of clinical disorders in iron balance.