Overview
Iron studies are often ordered in the setting of suspected cases of iron deficiency or iron overload. Assessment of iron stores is helpful in the patient who presents with non specific symptoms of lethargy.
Depending on the laboratory platform, assessment of iron studies includes measurement of:
- Serum iron
- Serum transferrin
(or total iron binding capacity; TIBC) / Transferrin saturation - Serum ferritin
- Soluble transferrin receptor
Test
Interpretation / Notes:
Serum iron
Considerable variation occurs within a day in individuals and assessment of serum iron alone provides little helpful clinical information.
Serum transferrin
(or total iron binding capacity; TIBC)
/ Transferrin saturation
Iron is bound to transferrin in the plasma. Total iron binding capacity (TIBC) is a direct measure of level of transferrin.Transferrin levels are reduced in inflammation.
Level of transferrin saturation is particularly helpful if assessment of early stages of iron overload with levels > 55% for males and > 50% for females indicative of iron overload (should be fasting level for more accurate assessment).
Serum ferritin
Small amount of circulating serum ferritin reflects body iron stores. Is now well established in assessment of iron stores
Normal range 15 – 300 ug/l
(reference ranges vary depending on the method used)
Levels < 15 ug/l reflect absent / reduced iron stores
Elevated levels may reflect iron overload but will be increased in liver disease, inflammation or malignant disease. In the presence of inflammation, a level of > 100 ug/l generally excludes iron deficiency
Soluble transferrin receptor
Transferrin receptors are present on cell surfaces and are responsible for the internalization of transferrin resulting in intracellular release or iron. In the absence of adequate iron stores, expression of tranferrin receptors increases.
The amount of soluble transferrin receptor closely reflects iron stores and is not affected by the inflammatory process. Increased levels of soluble transferrin receptor are also found in conditions of increased red cell turnover (e.g. haemolysis).
Interpretation
Interpretation of iron studies can be confusing with a number of the measures affected by iron therapy and acute phase response. See table below.
Suggestions for the “most helpful” test in the conditions described is in bold.
Further Questions?
The information presented in this fact sheet is intended as a general guide only.
Patients should seek further advice and information about their individual condition from their treating haematologist or doctor.
