SF level reflects the amount of storage iron in tissues. An elevated SF combined with elevated TS implies primary iron overload. Patients with hereditary hemochromatosis (HH) generally show increases in SF as adults, but a normal SF does not rule out the diagnosis of the disease. Children, young adults, and premenopausal females with HFE mutations may have had inadequate time to develop iron overload but may do so later in life. Serum ferritin levels observed in untreated patients with HH may range from 2000 to 3000 ng/mL.
SF alone is inadequate as the sole screening test for HH because it lacks the necessary sensitivity and specificity. SF is frequently elevated in persons with inflammation, cancer, or infection. SF is often ordered along with the serum iron and TIBC when iron overload is suspected. SF is also important in assessing the efficacy of the treatment of HH.
Upper limits of reference intervals for SF are 150 ng/mL for premenopausal women and 200 ng/mL for men and postmenopausal women.15 40 ng/mL is a typical lower limit for the reference interval.
SF is measured in serum using immunochemical methods such as enzyme-linked immunosorbent assay (ELISA), immunoradiometric assay, immunochemiluminescent assay, and immunofluorometry. SF tests are available as automated assays and in kit form.2
