Figure 7
Quantitative iron analysis and hepatic iron index (HII). The quantity of measured iron (left y-axis), in the context of the patient's age (x-axis), results in the hepatic iron index, defined by iron quantity in micrograms divided by the patient's age divided by the atomic weight of iron (55.8). An HII value of 1.9 (solid line) represents the traditional (pre-genetic testing) distinction between ‘homozygotes’ (HII >1.9) and ‘heterozygotes (HII <1.9). Current thought is that values >1.9 (dotted lines) reflect patients at risk for developing adverse consequences from iron overload and values <1.9 (hatched line) patients at little/no risk for adverse consequences from iron overload; many true C282Y homozygotes will have HII values below 1.9. The patient illustrated in Figure 2 is plotted as an example—if one assumes abnormal iron accumulation beginning early in life and continued iron accumulation, this patient will find themself with fibrosis-causing levels of liver iron while still in mid-adulthood if untreated.
