I am grateful to correspondent,Lynn, for drawing attention to something that had passed me by while I was ill. In distinguishing between iron deficiency and the anemia of chronic disorders, it is usually sufficient to measure the serum iron, the total iron binding capacity and the serum ferritin. In both, the serum iron will be low, but the iron binding capacity goes up in iron deficiency and down in the anemia of chronic disorders. Serum ferritin goes down in iron deficiency and is normal or raised in chronic disorders.
Sometimes patients have both iron deficiency and a chronic disorder, so how do you decide whether they should be given iron?
A few years ago the serum soluble transferrin receptor assay became available. This goes up in iron deficiency but is unaffected by chronic disorders.
However, this is not true for some hematological malignancies, especially for CLL. The serum soluble transferrin receptor level goes up in CLL and indeed is a measurement of tumor burden. So if you really are not sure whether someone with CLL is also iron deficient and the other tests won't help you, then the only way to find out for sure is to do a bone marrow biopsy and stain it for iron.