Iron Studies: Iron (Total), Iron-Binding Capacity (Total), Transferrin, and Iron Saturation
Synonym/Acronym
Iron: Fe; iron-binding capacity and iron saturation: TIBC, Fe Sat; transferrin: siderophilin, TRF.
Rationale
To monitor and assess iron levels related to blood loss, dietary intake and metabolism, storage disorders, and replacement therapy. To assist in diagnosing types of anemia such as iron deficiency.
Patient Preparation
Instruct the patient to fast for at least 12 hr before specimen collection for iron or transferrin and, with medical direction, to refrain from taking iron-containing medicines before specimen collection. There are no food, fluid, activity, or medication restrictions unless by medical direction for the TIBC and iron saturation. Specimen collection for iron studies should be delayed for several days after blood transfusion. Protocols may vary among facilities.
Normal Findings
Method: Spectrophotometry for iron and TIBC; nephelometry for transferrin.
| Iron | | |
|---|
| Age | Conventional Units | SI Units (Conventional Units × 0.179) |
|---|
| Newborn | 100–250 mcg/dL | 17.9–44.8 micromol/L | | Infant–14 yr | 40–105 mcg/dL | 7.2–18.8 micromol/L | | 15 yr–Adult | | | | Male | 75–175 mcg/dL | 13.4–31.3 micromol/L | | Female | 60–160 mcg/dL | 11–29 micromol/L |
Values tend to decrease in older adults. |
| Test | Conventional Units | SI Units (Conventional Units × 0.179) |
|---|
| TIBC | 250–450 mcg/dL | 45–81 micromol/L | | Transferrin-iron saturation % | 15%–50% | 15%–50% |
|
| Transferrin (Direct Measurement) |
|---|
| Age | Conventional Units | SI Units (Conventional Units × 0.01) |
|---|
| Newborn | 130–275 mg/dL | 1.3–2.75 g/L | | Infant–14 yr | 180–330 mg/dL | 1.8–3.3 g/L | | 15 yr–Adult | | | | Male | 215–365 mg/dL | 2.2–3.6 g/L | | Female | 250–380 mg/dL | 2.5–3.8 g/L |
|
Iron
Intervention may include chelation therapy by administration of deferoxamine mesylate (Desferal).
Study type: Blood collected in a gold-, red-, or red/gray-top tube; related body system: Circulatory system.
Iron plays a principal role in erythropoiesis, the formation and maturation of RBCs, and is required for Hgb synthesis. The human body contains between 4 and 5 grams of iron, about 65% of which is present in hemoglobin and 3% of which is present in myoglobin, the oxygen storage protein found in skeletal and cardiac muscle. A small amount is also found in cellular enzymes that catalyze the oxidation and reduction of iron. Excess iron is stored in the liver and spleen as ferritin and hemosiderin. Any iron present in the serum is in transit between the alimentary tract, the bone marrow, and available iron storage forms. Sixty to seventy percent of the body’s iron is carried by its specific transport protein, transferrin. TIBC and transferrin are sometimes referred to interchangeably, even though other proteins carry iron and contribute to the TIBC. For additional information about stored iron, refer to the study titled “Ferritin.”
Transferrin is a glycoprotein formed in the liver. Its role is the transportation of iron obtained from dietary intake or RBC breakdown; normally, one-third of available transferrin is saturated. Inadequate transferrin levels can lead to impaired Hgb synthesis and anemia. Transferrin is subject to diurnal variation, and it is responsible for the variation in levels of serum iron throughout the day. Normally, iron enters the body by oral ingestion; only 10% is absorbed, but as much as 20% to 30% can be absorbed in patients with iron-deficiency anemia. Unbound iron is highly toxic, but there is generally an excess of transferrin available to prevent the buildup of unbound iron in the circulation. Iron overload is as clinically significant as iron deficiency. An example of acute iron overload is the accidental poisoning of children caused by excessive intake of iron-containing multivitamins. Chronic iron overload can occur in patients receiving serial therapeutic transfusions of RBCs over time for treatment of various cancers, hemoglobinopathies such as sickle cell anemia, the thalassemias, and other hemolytic anemias.
Factors That May Alter the Results of the Study
- Drugs and other substances that may increase iron levels include blood transfusion products, chemotherapy drugs, iron preparations (e.g., epoetin alfa, ferrous sulfate, iron, iron dextran), methimazole, methotrexate, oral contraceptives, and rifampin.
- Failure to withhold iron-containing medications 24 hr before the test may falsely increase iron values.
- Drugs and other substances that may increase TIBC levels include mestranol and oral contraceptives.
- Drugs and other substances that may increase transferrin levels include carbamazepine, danazol, mestranol, and oral contraceptives.
- Drugs and other substances that may decrease iron levels include acetylsalicylic acid, allopurinol, cholestyramine, corticotropin, cortisone, deferoxamine mesylate, and metformin.
- Drugs and other substances that may decrease TIBC levels include asparaginase, chloramphenicol, corticotropin, cortisone, and testosterone.
- Drugs and other substances that may decrease transferrin levels include cortisone and dextran.
Other Considerations
- Gross hemolysis can interfere with iron test results.
- Transferrin levels are subject to diurnal variation and should be collected in the morning, when levels are highest.
Potential Nursing Problems: Assessment & Nursing Diagnosis
| Problems | Signs and Symptoms |
|---|
| Bleeding (blood loss—related to heavy menses, disease process with chronic blood loss [GI ulcer, malignancy], overuse of NSAIDs) | Altered level of consciousness, hypotension, increased heart rate, decreased Hgb and Hct, decreased serum iron, capillary refill greater than 3 sec, cool extremities, poor dietary selections | | Fatigue (related to decreased oxygenation associated with unhealthy RBCs secondary to inadequate iron) | Verbalization of fatigue, altered ability to perform activities of daily living due to lack of energy, shortness of breath with exertion, increasingly frequent rest periods, presence of fatigue after sleep, inability to adhere to daily routine, altered level of concentration, complaints of tiredness | | Nutrition(insufficient—related to inability to digest, metabolize, ingest foods; refusal to eat; increased metabolic needs associated with disease process; lack of understanding; unable to obtain healthy iron-rich foods) | Unintended weight loss; current weight is 20% below ideal weight; pale, dry skin; dry mucous membranes; documented inadequate caloric intake; subcutaneous tissue loss; hair pulls out easily; paresthesia | | Tissue perfusion (cerebral, peripheral, renal—related to inadequate cellular oxygen associated with unhealthy RBCs secondary to iron deficiency) | Confusion, altered mental status, headaches, dizziness, visual disturbances, hypotension, cool extremities, capillary refill greater than 3 sec, weak pedal pulses, altered level of consciousness, decreased urine output |
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Before the Study: Planning and Implementation
Teaching the Patient What to Expect
- Discuss how this test can assist in evaluating anemia and the amount of iron in the blood.
- Explain that a blood sample is needed for the test.
After the Study: Implementation & Evaluation Potential Nursing Actions
Treatment Considerations
- Resume usual diet, fluids, medications, or activity, as directed by the HCP.
Bleeding
- Assess the effects of blood loss by monitoring serum iron.
- Monitor and trend vital signs.
- Administer ordered blood or blood products and prescribed iron.
- Identify the cause of chronic blood loss, and assess stool for blood.
- Consider a dietary consult; assess for iron-rich foods and foods that inhibit absorption of iron.
Fatigue
- Monitor and trend CBC, Hgb, Hct, and iron.
- Monitor for shortness of breath and administer ordered oxygen with use of pulse oximetry.
- Assess for medical or psychological factors contributing to fatigue, prioritize and bundle activities to conserve energy, encourage frequent rest periods.
- Assess the ability to perform self-care, and assist as needed.
- Assess for adequate nutritional intake of iron-rich foods.
- Administer ordered blood and blood products and prescribed iron supplements as ordered.
- Monitor urine, stool, and sputum for bleeding.
Tissue Perfusion
- Blood loss can contribute to poor tissue perfusion.
- Monitor blood pressure, assess for dizziness, check skin temperature for warmth, and assess capillary refill and pulses.
- Monitor level of consciousness.
- Monitor urine output (to be in excess of 30 mL/hr).
- Ensure adequate fluid intake or administer ordered IV fluids.
- Administer ordered iron supplements.
Nutritional Considerations
- There are numerous factors that affect the absorption of iron, enhancing or decreasing absorption, regardless of the original content of the iron-containing dietary source.
- Explain to those with abnormally elevated or abnormally decreased iron levels the importance of reading food labels. Foods high in iron include meats (especially liver), eggs, grains, and green leafy vegetables.
- Note: Animal liver (e.g. beef, chicken, deer, lamb) is a nutrient dense food. Micronutrients, with the exception of vitamin D, are not produced by the body; they must be obtained from dietary sources. Liver is a rich source of vitamins and minerals, most notably providing significant amounts of iron, copper, folate, vitamin A, and vitamin B12. Regularly eating large amounts of animal liver can result in vitamin A toxicity and/or damage to the patient’s liver. The general recommendation commonly given by health care providers to adult patients is to consume no more than one to three and a half ounces (28 to 100 gm) of liver, once a week. Recommended portions depend on age and gender. Patients should also be aware of vitamin and mineral concentrations contained in dietary supplements that are taken regularly.
- Explain that iron levels in foods can be increased if foods are cooked in cookware containing iron.
- Explain how to either increase or avoid intake of iron and iron-rich foods depending on the specific condition. For example, a patient with hemochromatosis or acute pernicious anemia should be educated to avoid foods rich in iron. A patient with iron deficiency anemia should be educated to identify and consume foods rich in iron.
- Discuss how consumption of large amounts of alcohol damages the intestine and allows increased absorption of iron, as does a high intake of calcium and ascorbic acid.
- Explain that iron absorption after a meal is increased by factors in meat, fish, and poultry.
- Explain that iron absorption is decreased by the absence (gastric resection) or diminished presence (use of antacids) of gastric acid.
- Explain that phytic acids from cereals, tannins from tea and coffee, oxalic acid from vegetables, and minerals such as copper, zinc, and manganese interfere with iron absorption.
- Obtain an accurate nutritional history and assess attitude toward eating.
- Facilitate a dietary consult to evaluate current eating habits and best method of nutritional supplementation focusing on iron-rich foods.
- Monitor serum iron, assess swallowing ability, and encourage iron-rich cultural home foods.
Clinical Judgement
- Consider how to convey the importance of blood transfusion toward health when deemed a medical necessity.
Follow-Up and Desired Outcomes
- Acknowledges contact information provided for the U.S. Department of Agriculture’s resource for nutrition (www.choosemyplate.gov).
can be calculated as either (serum iron/TIBC value) × 100 or (serum iron × 100%)/TIBC.