Type of test Blood

 Normal findings

 Iron

 Male: 80-180 mcg/dL or 14-32 μmol/L (SI units) Female: 60-160 mcg/dL or 11-29 μmol/L (SI units)

Newborn: 100-250 mcg/dL Child: 50-120 mcg/dL

TIBC : 250-460 mcg/dL or 45-82 μmol/L (SI units)

Transferrin

Adult male: 215-365 mg/dL or 2.15-3.65 g/L (SI units) Adult female: 250-380 mg/dL or 2.5-3.8 g/L (SI units)

Newborn: 130-275 mg/dL Child: 203-360 mg/dL

Transferrin saturation

 Male: 20%-50% Female: 15%-50%

Test explanation and related physiology

Serum iron

Abnormal levels of iron are characteristic of many dis eases, including iron deficiency anemia and hemochromatosis. Seventy percent of iron in the body is found in the hemoglobin of red blood cells (RBCs). The other 30% is stored iron in the form of ferritin (p. 408) and hemosiderin. Iron is supplied by the diet. Iron is bound to a globulin protein called transferrin. When iron stores are low, transferrin levels increase. Transferrin is low when there is too much iron. Usually about one-third of the transferrin is used to transport iron. Because of this, the blood serum has considerable extra iron-binding capacity, which is the unsaturated iron-binding capacity (UIBC). The TIBC equals UIBC plus the serum iron measurement. Some laboratories measure UIBC, some measure TIBC, and some measure transferrin. The serum iron determination is a measurement of the quantity of iron bound to transferrin.

Iron-deficiency anemia is a result of reduced serum iron. Iron-deficiency anemia has many causes, including the following:

 • Insufficient iron intake

 • Inadequate gut absorption

 • Increased requirements (e.g., in growing children)

 • Loss of blood (e.g., menstruation, bleeding peptic ulcer)

 Iron deficiency results in decreased production of hemoglobin, which in turn results in small, pale (microcytic, hypochromic) RBCs. A decreased serum iron level, elevated TIBC, and low transferrin saturation (TS) value are characteristic of iron deficiency anemia.

Acute iron poisoning due to accidental or intentional over dose is characterized by a serum iron level that exceeds the TIBC. Chronic iron overload or poisoning is called hemochromatosis or hemosiderosis. Excess iron is usually deposited in the brain, liver, and heart and causes severe dysfunction of these organs. Massive blood transfusions also may cause elevated serum iron levels, although only transiently.

Total iron-binding capacity and transferrin

TIBC is a measurement of all proteins available for binding mobile iron. Transferrin represents the largest quantity of iron-binding proteins. Therefore TIBC is an indirect yet accurate measurement of transferrin. Ferritin is not included in TIBC because it binds only stored iron. TIBC is increased in 70% of patients with iron deficiency.

Transferrin is a negative acute-phase reactant protein. That is, in various acute inflammatory reactions, transferrin levels diminish. Transferrin also is diminished in the face of chronic illnesses, such as malignancy, collagen vascular diseases, or liver diseases. Hypoproteinemia is also associated with reduced transferrin levels.

TIBC varies minimally according to iron intake and is more of a reflection of liver function (transferrin is produced by the liver) and nutrition than of iron metabolism.

Total iron-binding capacity and transferrin saturation The percentage of transferrin and other mobile iron-binding proteins saturated with iron is calculated by dividing the serum iron level by the TIBC:

The normal value for TS is 20% to 50%. TS is decreased to less than 15% in patients with iron-deficiency anemia. It is increased in patients with hemolytic, sideroblastic, or megaloblastic anemias. TS is also increased in patients with iron overload or poisoning. Increased intake or absorption of iron (as in hemochromatosis) leads to elevated iron levels. In such cases, TIBC is unchanged; as a result, the percentage of TS is very high. UIBC has been proposed as an inexpensive alternative to transferrin saturation.

Chronic illness is characterized by a low serum iron level, decreased TIBC, and normal TS. Pregnancy is marked by high levels of protein, including transferrin. Because iron requirements are high, it is not unusual to find low serum iron levels, high TIBC, and a low percentage of TS in late pregnancy.

Contraindications

 • Patients with hemolytic diseases, because they may have an artificially high iron content Interfering factors

 • Recent blood transfusions may affect test results.

 • Recent ingestion of a meal containing high iron content may affect test results.

• Hemolytic diseases may be associated with an artificially high iron content.

* Drugs that may cause increased iron levels include chloramphenicol, dextran, estrogens, ethanol, iron preparations, methyldopa, and oral contraceptives.

* Drugs that may cause decreased iron levels include adrenocorticotropic hormone, chloramphenicol, cholestyramine, colchicine, deferoxamine, methicillin, and testosterone.

* Drugs that may cause increased TIBC levels include fluorides and oral contraceptives.

* Drugs that may cause decreased TIBC levels include ACTH and chloramphenicol.

Procedure and patient care

 • See inside front cover for Routine Blood Testing.

• Fasting: yes (12 hours)

• Blood tube commonly used: red

• Avoid hemolysis, because the iron contained in the RBCs will pour out into the serum and cause artificially high iron levels.

Abnormal findings

 Increased serum iron levels

- Hemosiderosis

- Hemochromatosis

- Hemolytic anemia

- Hepatitis

- Hepatic necrosis

- Lead toxicity

- Iron poisoning

- Massive blood transfusion

Decreased serum iron levels

- Insufficient dietary iron

- Chronic blood loss

- Inadequate absorption of iron

- Pregnancy (late)

- Iron deficiency anemia

- Neoplasia

- Chronic gastrointestinal blood loss

- Chronic hematuria

- Chronic heavy physiologic or pathologic menstruation

Increased TIBC or transferrin levels

- Oral contraceptives

- Pregnancy (late)

- Polycythemia vera

- Iron deficiency anemia

Decreased TIBC or transferrin levels

- Hypoproteinemia

- Inflammatory diseases

- Cirrhosis

- Hemolytic anemia

- Pernicious anemia

- Sickle cell anemia

Increased TS or TIBC saturation

- Hemochromatosis

- Hemosiderosis

- Acute iron overdose

- Hemolytic anemia

Decreased TS or TIBC saturation

- Iron deficiency anemia

- Chronic illnesses (e.g., malignancy)

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مواضيع ذات صلة

lactic acid (Lactate)

ischemia-modified albumin (IMA)

Platelet Indices and Platelet Count

Red Cell Distribution

Flow Cytometry

intrinsic factor antibody (IF ab)

insulin-like growth factor (IGF-1, Somatomedin C, Insulin-like growth factor binding proteins [IGF BP])

insulin assay

immunoglobulin quantification

Diagnosis of Familial Dyslipidemia

Lipid Profile

5-hydroxyindoleacetic acid (5-HIAA)