Iron/iron binding capacity - serum

Last updated: Wednesday, 17, March, 2004
Item Process
Specimen

5 mL blood in plain or lithium heparin tube.

Method

Iron - spectrophotometry.

Iron binding capacity: immunoassay of transferrin with expression of the result in µmol/L. Iron binding capacity is 2 x transferrin concentration.

Transferrin saturation: iron/iron binding capacity expressed as a decimal or as a percentage.

Reference Interval

Iron: 10-30 µmol/L
Iron binding capacity: 45-80 µmol/L
Transferrin saturation: 0.15-0.45 (15-45%)
Transferrin: 1.7-3.0 g/L

Application

Investigation of suspected iron deficiency or iron overload; serum ferritin is the preferred method for assessing iron stores. See Ferritin.

The tests are not appropriate and may be misleading in patients receiving iron therapy.

Assessment of patients with acute iron poisoning.

Interpretation

This may be complicated by the presence of an acute phase response, which is associated with decreased iron and iron binding capacity (with increased ferritin). Hepatocellular disease can have a similar effect. When iron deficiency may co-exist with an acute phase response assay of serum soluble transferrin receptors may be helpful. See Table 3. In acute iron poisoning, iron levels are often >60 µmol/L, with transferrin saturation >100%. Toxicity can occur with lower levels if absorption is continuing at the time of specimen collection.

Reference

Brugnara C. Clin Chem 2003; 49(10): 1573-1578.