Iron status indicators: hello new, goodbye old?

A recent Brief report1 highlighted the clinical use of the reticulocyte hemoglobin content (CHr) in the assessment of iron status. It identified a strong correlation between CHr and an assessment of stainable bone marrow iron stores.

The conclusion that CHr could predict the degree of stainable iron perpetuates the misunderstanding that has dogged the assessment of “iron status” for many decades. It fails to recognize that this status can have different levels in different parts of the iron metabolic process. Stainable iron stores give crude and imprecise estimates of the insoluble ferric hydroxide complexes deposited in the reticuloendothelial system. Whether or not this is a “store” or simply iron taken out of active metabolic employment is another matter. CHr, on the other hand, is a direct reflection of recent hemoglobin synthesis in developing red cells. It is a measure of the adequacy of the rate of iron supply and this, as has been amply shown in renal anemia, can be compromised even when there is iron on deposit in the stores. CHr is a new and valuable parameter in its own right.

The need to assess stainable iron owes more to tradition than to clinical diagnostic science. With the availability of parameters, such as CHr, that reflect a pathophysiologic reality, it is time to dispense with “Fool's Gold” standards (iron pyrites, a mineral deposit that looks like gold).