Iron is necessary for the production of Hb. Iron is contained in several components. Transferrin (also called siderophilin), a transport protein largely synthesized by the liver, regulates iron absorption. High levels of transferrin relate to the ability of the body to deal with infections. Total iron-binding capacity (TIBC) correlates with serum transferrin, but the relation is not linear. A serum iron test without a TIBC and transferrin determination has very limited value except in cases of iron poisoning. Transferrin saturation (TSAT) is a better index of iron saturation; it is evaluated as follows:

The combined results of transferrin, iron, and TIBC tests are helpful in the differential diagnosis of anemia, in assessment of iron-deficiency anemia, and in the evaluation of thalassemia, sideroblastic anemia, and hemochromatosis (Table 2.6).

Iron

• Adult men: 70–175 μg/dL or 12.5–31.3 μmol/L

• Adult women: 50–170 μg/dL or 8.9–30.4 μmol/L

• Children: 50–120 μg/dL or 9.0–21.5 μmol/L

• Newborns: 100–250 μg/dL or 17.9–44.8 μmol/L

TIBC

• Men: 250–450 μg/dL or 44.8–76.1 μmol/L

• Women: 250–450 μg/dL or 44.8–76.1 μmol/L

Transferrin

• Adults: 215–380 mg/dL or 2.15–3.8 g/L

• Children: 203–360 mg/dL or 2.0–3.6 g/L

• Newborns: 130–275 mg/dL or 1.3–2.7 g/L

Transferrin (iron) saturation

• Men: 20%–50%

• Women: 15%–45%

1. Obtain a venous blood sample of 5 mL using a red-topped tube. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.

2. Place the specimen in a biohazard bag. Serum is needed for these tests.

1. Increased transferrin is observed in:

   1. Iron-deficiency anemia (uncomplicated)

   2. Pregnancy

   3. Estrogen therapy

2. Decreased transferrin is found in:

   1. Microcytic anemia of chronic disease

   2. Protein deficiency or loss from burns or malnutrition

   3. Chronic infection

   4. Acute liver disease

   5. Renal disease (nephrosis)

   6. Genetic deficiency, hereditary atransferrinemia

   7. Iron-overload states (hemochromatosis)

3. Decreased iron occurs in:

   1. Iron-deficiency anemia

   2. Chronic blood loss

   3. Chronic diseases (e.g., lupus, RA, chronic infections)

   4. Third-trimester pregnancy and progesterone birth control pills

   5. Remission of pernicious anemia

   6. Inadequate absorption of iron

   7. Hemolytic anemia (PNH)

4. Increased iron occurs in:

   1. Hemolytic anemias, especially thalassemia, pernicious anemia in relapse (not hemolytic anemias)

   2. Acute iron poisoning (children)

   3. Iron-overload syndromes

   4. Hemochromatosis, iron overload

   5. Transfusions (multiple), intramuscular iron, inappropriate iron therapy

   6. Acute hepatitis, liver damage

   7. Vitamin B₆ deficiency

   8. Lead poisoning

   9. Acute leukemia

   10. Nephritis

5. Increased TIBC is found in:

   1. Iron deficiency

   2. Pregnancy (late)

   3. Acute and chronic blood loss

   4. Acute hepatitis

6. Decreased TIBC is observed in:

   1. Hypoproteinemia (malnutrition and burns)

   2. Hemochromatosis

   3. Non–iron-deficiency anemia (infection and chronic disease)

   4. Cirrhosis of liver

   5. Nephrosis and other renal diseases

   6. Thalassemia

   7. Hyperthyroidism

7. The iron saturation index is increased in:

   1. Hemochromatosis

   2. Increased iron intake

   3. Thalassemia

   4. Hemosiderosis

   5. Acute liver disease

8. The iron saturation index is decreased in:

   1. Iron-deficiency anemias

   2. Malignancy (standard and small intestine)

   3. Anemia of infection and chronic disease

   4. Iron neoplasms

Pretest Patient Care

1. Explain test purpose and procedure.

2. Draw fasting blood in the morning, when levels are higher.

3. Draw iron sample before iron therapy is initiated or blood is transfused.

4. If the patient has received a transfusion, delay iron testing for 4 days.

5. Avoid any iron-chelating drug (e.g., deferoxamine).

6. Avoid sleep deprivation and extreme stress, which cause lower iron levels.

7. Note on laboratory slip or computer screen whether the patient is taking oral contraceptives or estrogen therapy or is pregnant.

8. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

1. Many drugs affect test outcomes (see Appendix E).

2. Drugs that may cause increased iron include ethanol, estrogens, and oral contraceptives.

3. Drugs that may cause decreased iron include some antibiotic drugs, aspirin, and testosterone.

4. Hemolysis of the blood sample interferes with testing.

5. Iron contamination of glassware used in testing can give high values.

6. Menstruation causes decreased iron; iron is elevated in the premenstrual period.

7. There is a diurnal variation in iron: normal values in the morning, lower in midafternoon, very low in the evening.

8. Serum iron and TIBC may be normal in iron-deficiency anemia if the Hb is more than 9.0 g/dL (or more than 90 g/L).