et al 1994 Telfer PTl, 2000 Davis BA, et al. Importantly, however, at least five studies have shown an association between the control of serum ferritin and prognosis ( Gabutti V and Piga A. Therefore although there is a broad correlation between serum ferritin level and liver iron, the prediction of iron loading from serum ferritin can be unreliable ( Olivieri 1995). In thalassaemia intermedia, serum ferritin tends to underestimate the degree of iron overloading ( Pootrakul 1981). A sudden and unexpected rise in ferritin level should prompt a search for hepatitis, other infections or inflammatory conditions. Day-to-day variations are particularly marked: high degrees of iron loading, inflammation, hepatitis and/or liver damage may falsely increase serum ferritin, while vitamin C deficiency may depress it.
Up to a value of about 3,000 µg/L serum ferritin is secreted in an iron-free form from macrophages, but above this value increasing proportions of iron-laden ferritin ‘leaks’ from hepatocytes ( Worwood, 1980 Davis, 2004). This is a relatively easy test to perform, well established, generally correlating with body iron stores and prognostically relevant in thalassaemia major. Regular blood transfusion therapy therefore increases iron stores to many times the norm unless chelation treatment is given. Thus, irrespective of whether the blood used is packed, semi-packed or diluted in additive solution, if the whole unit is given, this will approximate to 200 mg of iron intake.Īccording to the recommended transfusion scheme for thalassaemia major, the equivalent of 100–200 ml of pure RBC per kg per year are transfused (equivalent to 116–232 mg of iron per kg body weight per year or 0.32–0.64 mg/kg/day). In case organisational or other difficulties do not allow such estimations, a rough approximation can be made based on the assumption that 200 mg of iron is contained in each donor unit. Simple calculations, such as those described in the Blood Transfusion Chapter of this book, can provide the treating physician with this information. Knowledge of the rate of iron loading from transfusion to as high a level of accuracy as possible will contribute significantly to the formulation of chelation therapy appropriate for each patient.
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