The iron studies are a group of routine haematology tests that are used primarily in the investigation of anaemia but should also be ordered on suspicion of iron deficiency or perhaps some other obscure disease(s). The standard component tests run by Awanui labs include serum iron, ferritin, transferrin, and transferrin saturation.
Serum iron
Is a comparatively useless test, mostly on account of the confusion it causes.
It might be low in iron deficiency, but it is frequently normal.
Hereditary haemochromatosis (HFE) infrequently causes an elevated serum iron.
Serum ferritin
Ferritin is a largely intracellular protein the is concentrated in the hepatocytes and cells of the reticuloendothelial system (read ‘the spleen’). The serum concentration is proportional to the cellular concentration in the usual physiological equilibrium. It is an acute phase reactant. This is the most useful of the tests as it is the assay that reports on iron stores.
Significantly decreased ferritin is diagnostic of iron deficiency.
Elevated ferritin is typically a marker of inflammation. It may also indicate significant body iron stores, typically in response to intravenous supplementation. Extreme elevation is seen in haemophagocytic lymphohistiocytosis, but may be caused by a severe inflammatory state, malignancy, or HFE.
Serum transferrin
In contrast to ferritin, transferrin, as the name implies, is the protein responsible for shuttling iron from its intracellular (mostly hepatic) storage to the bone marrow for use in haematopoesis. Transferrin, and transferrin saturation are measures of tissue iron supply.
Transferrin increases in response to iron deficiency, in which case ferritin is low so you have already diagnosed the patient…
Low transferrin is seen in iron overload and inflammatory states, as well as malignancy and renal disease. Iron overload can be identified by an elevated transferrin saturation.
Transferrin saturation
Maybe serum iron is not so useless after all because it is used to calculate the transferrin saturation. The below equation is also taken from Awanui labs:
Reference ranges
- Iron: 10-30μmol/L
- Ferritin: generally >25μmol/L
- Transferrin: 2.0-3.2g/L (3.6 in young females)
- Transferrin saturation: 16-45%