Q. Are anemia of chronic disease and iron deficiency anemia technically both iron-deficient conditions? Is it just that pure iron deficiency is caused by no iron, whereas anemia of chronic disease is more complicated? I don’t get what we’re supposed to get out of comparing the TIBC and ferritin level in these two anemias.
A. Yes – both iron deficiency anemia and anemia of chronic disease are technically iron deficiencies (if you equate “iron deficiency” with a low serum iron). IDA is a plain old iron deficiency – that’s the only problem. Everything else would work just fine – it’s just that the supply of iron is low.
In ACD, however, there’s a ton of stuff going on (and I don’t think we really completely understand everything yet either). The iron seems to be absorbed okay, for the most part, but it can’t get from the storage forms (ferritin, hemosiderin) to the red cells. Hepcidin is a major mediator of the process as we discussed here and here.
So with the lab tests, we’re just trying to distinguish between the two diseases (because at times they can look similar morphologically). Both have a low serum iron, so that doesn’t help you. In ACD, the ferritin is high, whereas in IDA, the ferritin is low (unless the patient has some other condition that makes ferritin go up – like systemic inflammation or something). If the ferritin is low, you can be sure it’s IDA. If it’s normal or high, it could be either IDA (with some other condition going on as well) or ACD.
The TIBC is high in IDA (which makes sense – there’s little iron around, so the capacity for binding iron increases). The TIBC is normal or decreased in ACD, for reasons that aren’t entirely clear. It may be that the production of transferrin goes down in ACD, which would make the TIBC stay normal (or decrease).
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