- Serum iron is low in both conditions, of course (that's why both conditions can lead to a microcytic anaemia!).
- TIBC is high in iron deficiency, since the body is putting out as many transferrin receptors as possible to scavenge any little bit of left-over iron. In ACI, on the other hand, the body wants as little iron as possible in circulation, and so it down-regulates the amount of transferrin it produces - TIBC is thus low.
- % sat is low in both states, although it is usually a little less low in ACI, since the TIBC is low in this condition too.
- Serum ferritin, like TIBC, is also helpful in differentiating the two conditions. In iron deficiency, it will obviously be low, since the iron stores are depleted. In ACI, however, iron stores are normal (this is where the iron is 'hidden'), and the reading may even be high, since the inflammation characteristic of ACI increases all acute phase proteins.
Thus, in summary, TIBC and serum ferritin are the two most helpful biochemical values in telling ACI apart from iron deficiency anaemia. In the latter condition, TIBC is high and ferritin low; the opposite obviously applies in the case of ACI.