Transferrin saturation has high biological variability and low sensitivity to detect HFE-related hemochromatosis [108] and a retrospective review of outpatient referrals for elevated serum ferritin found 64% of patients with a serum ferritin threshold over 1000 μg/L did not have iron overload on biopsy [109]. This evidence concerns the gene TF and hemochromatosis type 1.