| General Overview of Testing Tests for evaluating iron metabolism are generally used as initial or screening tests for hereditary hemochromatosis (HH) as they will detect the phenotypic expression of HH. These tests include serum iron (SI), transferrin (Tf) or total iron binding capacity (TIBC), serum ferritin (SF), and unsaturated iron binding capacity (UIBC).The serum ferritin assay is also used to assess the effectiveness of HH treatment.Molecular (DNA) analyses for HFE mutations are considered to be confirmatory tests for HH which may be ordered reflexively in patients with elevated iron results. Laboratories should establish their own reference intervals for assays of iron metabolism. In general, reference intervals vary by sex and by method used for the assays discussed in the following section. Typical reference intervals are included in the following sections for instructive purposes only and should not be used for evaluating actual patient data.The results of laboratory tests assessing iron metabolism should be interpreted with caution because a number of pre-analytical and physiologic factors can affect the results. Repeating elevated test results on fasting specimens is often advisable. | View Page |
| Which laboratory assay is considered to be a confirmatory test for hereditary hemochromatosis (HH)? | View Page |
| Storage Iron Storage forms normally comprise approximately 27% of total body iron. Stored iron provides a source of iron when physiologic demand is high, such as in blood loss, pregnancy, and periods of rapid growth. Storage compounds include ferritin and hemosiderin. Ferritin is a protein-bound, water-soluble, mobilizable storage compound and is the major source of stored iron. Hemosiderin is a water-insoluble form that is less readily available for use. When the amount of total body iron is relatively low, storage iron consists predominately of ferritin. When iron stores are increased, hemosiderin predominates. Unlike ferritin, hemosiderin stains with the Prussian blue stain (Perls reaction) and may be observed in tissues. | View Page |
| What is a mobilizable, water-soluble form of storage iron that is bound to protein? | View Page |
| What is the protein that carries iron in the blood plasma? | View Page |
| Altered Iron Absorption Hereditary hemochromatosis (HH) is a genetic disorder characterized by iron overload as a result of increased iron absorption. As iron absorption increases, the amount of iron bound to transferrin and transported in the plasma subsequently increases.With no available mechanism for excreting excess absorbed iron, normal iron storage sites become overloaded, resulting in ferritin levels that far exceed normal. As a result, iron is deposited in the parenchymal cells of the liver, pancreas, pituitary, heart, synovium, and other tissues with high concentrations of transferrin receptors. Iron in excess of normal cellular ferritin stores contributes to the generation of free radicals and reactive oxygen intermediates that cause cell damage to organs and tissues. This process results in the clinical condition known as iron overload, a hallmark feature of HH. | View Page |
| What laboratory test reflects circulating iron that is bound to transferrin? | View Page |
| Serum Ferritin Serum ferritin (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 and premenopausal females with HFE mutations may have had inadequate time to develop iron overload, but may do so later in life.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 is assessing the efficacy of treatment of HH.Upper limits of reference intervals for SF are 200 ng/mL for premenopausal women and 300 ng/mL for men and postmenopausal women. 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) | View Page |
| Why is serum ferritin (SF) a less than optimal screening test for hereditary hemochromatosis (HH)? | View Page |
| Initial Treatment Phlebotomy is considered the treatment of choice for patients with iron overload due to hereditary hemochromatosis (HH). Each unit of blood contains approximately 200 to 250 mg of iron. As erythrocytes are removed by phlebotomy, iron stores are mobilized and utilized in the production of new, circulating erythrocytes. Through periodic phlebotomies, stored iron is removed until iron-deficient erythropoiesis is induced. The initial, or iron reduction, phase of treatment typically consists of removing one unit (450 mL) of whole blood once or twice weekly. Prior to beginning phlebotomy, the patient’s hemoglobin and hematocrit must be checked to ensure that the patient is not anemic. A sample for serum ferritin is also collected at this time.Initial treatment goals include inducing iron deficient hematopoiesis without the development of debilitating symptoms of anemia. A hemoglobin concentration of 10.0 to 12.0 g/dL is often used as a target range. The initial treatment phase continues until excess stored iron is removed and ferritin levels decrease to approximately 50 ng/mL. (13) Ferritin and hemoglobin levels are periodically monitored during this phase. The number of phlebotomies needed to reduce iron levels and induce anemia is related to the degree of initial iron overload. Patients may be referred to a hematologist or gastroenterologist during the initial treatment phase. Many patients receive therapeutic phlebotomy services in a hospital or doctor’s office, but patients may also undergo phlebotomy at a blood center. Blood collected from persons with HH may be used for transfusion or as blood products if it has been collected from a facility with an approved variance from the US Food and Drug Administration. Not all blood centers have applied for or been granted this variance.(14)The initial treatment phase continues until excess stored iron is removed and ferritin levels decrease to approximately 50 ng/mL. Removal of excess stored iron may take from one month to three years. | View Page |
| Maintenance Therapy Lifelong treatment of hereditary hemochromatosis (HH) is needed to keep iron at low levels. Without regular treatment, iron stores will re-accumulate. The primary care physician may manage patient care during long-term maintenance. Long-term maintenance typically consists of removal of an average of 2 to 6 units of whole blood yearly, although this number is variable. Monitoring of hemoglobin and serum ferritin levels determine the frequency of phlebotomy. Serum ferritin levels should be maintained at concentrations of no more than 50 ng/mL. (10,13)) | View Page |
| How long should therapy continue for patients with hereditary hemochromatosis (HH)? | View Page |