MATHEMATICAL APPROACH FOR ESTIMATING IRON NEEDS IN HEMODIALYSIS-PATIENTS ON ERYTHROPOIETIN THERAPY

Functional iron deficiency occurs when recombinant human erythropoieti n (rHuEPO) accelerates erythropoiesis to an extent that the iron avail ability cannot meet the anticipated demand. Such a phenomenon will red uce the optimal response to rHuEPO. To estimate the iron needs of func tional iron deficiency in hemodialysis patients on rHuEPO therapy, we utilized a mathematical method. Forty hemodialysis patients were exami ned in the study, and all had a baseline serum ferritin (SF) level >10 0 mu g/l. They were stratified into patients with a transferrin satura tion (TfS) value greater than or equal to 25% (group I) and those belo w this value (group II). The treatment protocol consisted of rHuEPO th erapy in the two groups for 6 months and iron supplement only in group II. The target hemoglobin level was 10.5 g/dl, and iron metabolism in dices were analyzed prior to and following therapy. The results showed (1) in group I (n = 20) hemoglobin rose from 7.5 +/- 0.9 to 10.7 +/- 0.7 g/dl (p < 0.01) and the mean SF level declined from 1,583 +/- 997 to 968 +/- 664 mg (p < 0.01); (2) in group II (n = 20) hemoglobin also increased from 7.8 +/- 0.9 to 10.6 +/- 0.8 g/dl (p < 0.01) following iron supplement, while the SF rose from 183 +/- 70 to 326 +/- 125 mg ( p < 0.01); (3) TfS was significantly elevated in group II following ir on therapy (18.9 +/- 4.8 vs. 34.5 +/- 9.1%, p < 0.01), and (4) the nom ogram showed a sensitivity of 80%, a specificity of 100%, a positive p redictive value of 100%, and a negative predictive value of 83% in est imating the iron status before rHuEPO therapy. We conclude that SF lev els reflect iron stores and that TfS < 25% is an index of functional i ron deficiency. Iron supplementation is not necessary in patients with SF >100 mu g/l and TfS greater than or equal to 25%. It seems rationa l to provide intravenous iron in EPO-resistant patients with functiona l iron deficiency (SF >100 mu g/l, TR <25%). This paper illustrates th e importance that accurate assessment of iron needs by a mathematical method would enhance treatment efficacy and avoid iron overload in hem odialysis patients on rHuEPO therapy.