Investigation of subjects with abnormal iron studies: role of the hepatic iron index

Genetic haemochromatosis is a common disorder resulting in increased iron deposition in the liver and other organs but can be difficult to diagnose. The aim of this study was to assess the diagnostic value of the conventional tests for iron overload (percentage saturation of transferrin, serum ferritin and grading of iron staining on liver biopsy) and compare these with the newer quantitative biochemical measurements of liver iron.

A retrospective analysis was made of 108 consecutive patients referred for quantitative liver iron measurements. Iron studies were obtained in 66 of the 108 subjects of whom 60 had abnormal screening tests defined as percent saturation of transferrin (> 60%) and/or ferritin > 350 micrograms/L for females and > 450 micrograms/L for males. Based on clinical features, biochemical data and treatment outcome these 60 subjects were classified as either genetic haemochromatosis, nongenetic haemochromatosis or indeterminate. One patient with treated genetic haemochromatosis was excluded from subsequent analysis.

Although the serum ferritin (p < 0.002), percentage saturation of transferrin (p < 0.001), histological iron grade (p < 0.0001) were significantly higher in the genetic haemochromatosis than nongenetic haemochromatosis group there was considerable overlap. Similarly for the hepatic iron concentration (HIC) (p < 0.0001) overlap occurred. The hepatic iron index (HIC/age) gave the best separation with only three cases being misclassified. A correlation between the HII and histological iron index (visualised iron score corrected for age) in 15 subjects gave an r value of 0.72.

Based on this study we feel that in addition to visual grading of iron in liver biopsies, the hepatic iron index is helpful in establishing a diagnosis of genetic haemochromatosis.