title: Mathematical approach for estimating iron needs in hemodialysis patients on erythropoietin therapy.
abstract: Functional iron deficiency occurs when recombinant human erythropoietin (rHuEPO) accelerates erythropoiesis to an extent that the iron availability cannot meet the anticipated demand. Such a phenomenon will reduce the optimal response to rHuEPO. To estimate the iron needs of functional iron deficiency in hemodialysis patients on rHuEPO therapy, we utilized a mathematical method. Forty hemodialysis patients were examined in the study, and all had a baseline serum ferritin (SF) level > 100 microg/l. They were stratified into patients with a transferrin saturation (TfS) value > or = 25% (group I) and those below this value (group II). The treatment protocol consisted of rHuEPO therapy 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 indices 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 iron therapy (18.9 +/- 4.8 vs. 34.5 +/- 9.1%, p < 0.01), and (4) the nomogram showed a sensitivity of 80%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 83% in estimating the iron status before rHuEPO therapy. We conclude that SF levels reflect iron stores and that TfS < 25% is an index of functional iron deficiency. Iron supplementation is not necessary in patients with SF > 100 microg/l and TfS > or = 25%. It seems rational to provide intravenous iron in EPO-resistant patients with functional iron deficiency (SF > 100 microg/l, TfS < 25%). This paper illustrates the importance that accurate assessment of iron needs by a mathematical method would enhance treatment efficacy and avoid iron overload in hemodialysis patients on rHuEPO therapy.
authors.affiliation: Department of Medicine, Veterans General Hospital and National Yang-Ming University, Taipei, Taiwan.
authors.forename: D C
authors.initials: DC
authors.lastname: Tarng
authors.forename: T P
authors.initials: TP
authors.lastname: Huang
authors.forename: T W
authors.initials: TW
authors.lastname: Chen
mesh_terms: D000740:Anemia / Q000188:drug therapy* / Q000209:etiology; D018798:Anemia, Iron-Deficiency / Q000209:etiology* / Q000517:prevention & control; D004921:Erythropoietin / Q000627:therapeutic use*; D005260:Female; D005293:Ferritins / Q000097:blood; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007501:Iron / Q000378:metabolism*; D019190:Iron Overload / Q000517:prevention & control; D007676:Kidney Failure, Chronic / Q000150:complications / Q000628:therapy*; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D011237:Predictive Value of Tests; D011994:Recombinant Proteins; D006435:Renal Dialysis; D012680:Sensitivity and Specificity
chemical_list: D006454:Hemoglobins; D011994:Recombinant Proteins; D004921:Erythropoietin; D005293:Ferritins; D007501:Iron