Iron level differentiation

[nurselove757]

I am having a hard time figuring out the difference between serum iron and serum ferritin. I do know that serum iron is the iron level circulating in the blood, where serum ferritin is the iron that is "stored." I still don't know what this mean.

Also, how are these clinically significant in clinical practice?

[KatieMI, BSN, MSN, RN]

Ok,

You've got iron, meaning ion Fe3+. From food, from a dead erythrocyte, from another dead cell. You need to store it, transfer it where it is needed, and use it.

Ferritin is a storage form in liver, fat, bone marrow and some other cells. It binds and stores iron till it is needed. It is made in liver, so the level goes down if liver is failing. It is also an indirect indicator of inflammation (if there is inflammation, more cells are dying and destroyed, therefore more iron is released, and more ferritin is needed).

Transferrin is a liver-made protein which takes iron up and transports it where it is needed.

Total serum iron is just a sum of all iron in serum sample and doesn't speak much.

TIBS (total iron binding capacity) means iron bound by transferrin, or so-called "labeled pool". If it is low and transferrin is high, then there is a lot of need of iron and not much of it (anemia).

An article to start with

https://en.m.wikipedia.org/wiki/Human_iron_metabolism

Try to think about it as about factory and supply to make things easier.

[Corey Narry, MSN, RN, NP]

These are basically components of a diagnostic work-up when you are ruling out the cause of a microcytic anemia (low Hgb and MCV). You would order Serum Iron, Ferritin, and Total Iron Binding Capacity. Iron deficiency anemia is one of the causes of microcytic anemia as well as anemia of chronic disease, thalassemias, and sideroblastic anemia. The components help shed light on what process is going on.

For a more detailed discussion of how these tests are used in practice, look at this video:

There is a bullet point discussion of this on the Hematology section of : https://www.agilemd.com/partners/ucsf-hospitalist-handbook, which I always have on my smartphone.