In hereditary hemochromatosis, the measurement of the liver iron content is the "gold standard" in determining iron overload. The accumulation of iron progresses with time. To assess the iron overload independently from the age of the patient, Bassett, Halliday and Powell (1) introduced the hepatic iron index, that is, the liver iron content in micromoles per gram of dry weight, divided by the age of the patient in years. They found homozygous hemochromatosis subjects to have values >2, whereas heterozygotes and patients with liver disease had values <2. If the liver iron content were expressed as micrograms per milligram of protein, this discriminatory value would be 0.224.
We have calculated the hepatic iron index in our hereditary hemochromatosis patients and found it, indeed, to be > 0.224 (2). However, in two patients with secondary hemochromatosis (caused in one patient by HbE-thalassemia and transfusional siderosis and caused by aplastic anemia and transfusional siderosis in the other patient) the hepatic iron index was 1.2 and 0.53, respectively (Table 1). Therefore the hepatic iron index indicates severe iron overload, but it is not specific for hereditary hemochromatosis. Calculation of the hepatic iron index in larger groups of patients and controls will be necessary to determine sensitivity and specificity of this parameter.