Methods for evaluating iron stores and efficacy of chelation in transfusional hemosiderosis

An accurate determination of the total amount and distribution of body iron stores is essential for prognostic purposes and to evaluate the efficacy of chelation therapy. In the clinical setting, a rough estimate of the total body iron burden may be obtained in patients with transfusion-dependent anemias by calculating the amount of blood administered plus the amount absorbed by the gastrointestinal route, which is influenced by the level of Hb and by bone marrow activity. An increase in serum iron and a decrease in total iron binding capacity are early indicators of iron overload, but their sensitivity and specificity are not very high. In normal individuals, serum ferritin correlates well with iron stores, as measured by phlebotomy, and with directly measured liver iron. However, plasma ferritin, being an acute phase reactant, is increased in cases of chronic disease, disseminated malignancy, or inflammatory disorders. Non-transferrin bound iron, i.e. iron that circulates in plasma unbound to transferrin, is potentially toxic since it is capable of taking part in free radical-mediated reactions that result in irreversible tissue damage. This iron can be measured with a HPLC based assay. At present the most accurate way of estimating the iron burden is by direct measurement of iron concentration in tissues. The liver is the most accessible. The measurement is done by atomic absorption spectrometry on ashed or lyophilized samples obtained by needle biopsy, and correlates well with the total amount of blood transfused and with the extent of hepatic fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)