Jenkins PG, Mazumdar DC
Rapid change in iron saturation after initiation or cessation
of intravenous EPO in hemodialysis patients
NKF 6th Spring Clinical Meeting (Dallas)
Am J Kidney Dis
(Apr) 29:A9 1997
There has been a recent appreciaion of the fact that the tests we use to
define iron status are fairly inaccurate when used in patients with ESRD.
This study evaluated the change in iron parameters thqat occur with
initiaition or cessation of EPO therapy.
Serum iron, transferrin saturation (TSAT), serum ferritin and hematocrit were
measured before, and then 25 days after an initiation or cessation of iv EPO
therapy in 20 hemodialysis patients. Significant changes were found for the
serum iron and TSAT. Specifically, the TSAT decreased by 27 +/- 20% with
initiation of EPO, and increased by 24 +/- 20% with cessation of EPO. The
authors
concluded that the rapid change in TSAT after changes in EPO therapy render
the tests very difficult to use.
Comment: This is an interesting small study which clearly documents an
interesting phenomenon. When EPO therapy is initiated, erythropoiesis
accelerates significantly. This induces a mismatching of iron supply and
demand, leading to what has been termed functional iron deficiency. This
occurs even in the presence of normal iron stores, as has been demonstrated
in normal volunteers. In dialysis patients, this increased demand for iron
induced by EPO is coupled with reduced iron stores caused by chronic blood
loss. The result is a remarkably high incidence of functional iron
deficiency.
While the study is interesting, the conclusions of the authors are incorrect.
The changes in iron indices that they have noted are real. The patients have
developed functional iron deficiency. We have recently demonstrated this
phenomenon at the level of the reticulocyte, using flow cytometry to
demonstrate depletion of hemoglobin soon after increases in EPO dosing
(Kidney Int in press). This is an important clinical phenomenon, since
EPO
dose increases may occasionally be completely ineffective due to the
induction of iron deficiency.
(Stephen Fishbane, M.D., Winthrop University Hospital, Mineola, NY)
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NKF 6th Spring Clinical Meeting (Dallas)
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