Judgement of measured values of intestinal iron absorption

The value of a medicinal iron preparation is influenced by several factors e.g. therapeutical efficacy, frequency of side effects, and prescriptions for intake. Since the accurate quantitation of therapeutical efficacy is difficult to establish, the value of fractional intestinal absorption of iron, which is a prerequisite for the effect on haemoglobin regeneration, represents a useful criterion for that particular factor. When intestinal absorption is investigated the selection of subjects is of importance. Studies should be performed on subjects with iron deficiency since the adaptation of intestinal absorption to the body's need is the basis of oral iron supplementation. Different methods have been used to assess intestinal absorption, some of which give almost identical results or show a close correlation. However, mixing data from different investigations in order to convert semi-quantitative values obtained from plasma iron tolerance curves into amounts of absorbed iron by means of regression equations estimated from studies on different subjects and under different conditions may lead to considerable uncertainties of the calculated results. Even more difficult to evaluate is the relation between fractional absorption and costs of therapy, since there are additional factors influencing the duration of supplementation and therefore the total amount of iron necessary.