Transferrin Saturation

Iron is in its Fe(III) form bound to apotransferrin: the complex is called transferrin. Normally only about one third of the iron binding sites of transferring are occupied by Fe(III). The additional amount of iron that can be bound is the unsaturated (or latent) iron binding capacity (UIBC). TIBC is a measurement for the maximum iron concentration that transferrin can bind. Serum TIBC varies in disorders of iron metabolism. In iron deficiency anaemia (IDA), the TIBC is elevated and the transferrin saturation is lowered to 15 % or less. Low serum iron associated with low TIBC is characteristic of the anaemia of chronic disorders, malignant tumours, and infections. An alternative to TIBC is calculation of the transferrin saturation. Low transferrin saturation indicates IDA; while transferrin saturations >50% indicate iron overload.
The following equation is used in the laboratory to calculate transferrin saturation:
Transferrin saturation (%) = (Iron / TIBC) x 100