Iron Status In Continuous Ambulatory Peritoneal Dialysis Patients

Nutrition Research Newsletter, Sept, 1999 by Somnuek Domrongkitchaiporn, Boonchai Jirakranont, Kalayanee Atamasrikul

The use of recombinant human erythropoietin has made it possible to correct anemia in most end-stage renal disease patients. The downfall is that this is frequently associated with the development of iron deficiency. Iron status indices in continuous ambulatory peritoneal dialysis (CAPD) patients are limited and the reliability of the current indices is unknown. Iron deficiency is the most common cause of suboptimal response or resistance to erythropoietin therapy. Absence of stainable iron in bone marrow smear has been considered as the "gold standard" for the diagnosis of iron deficiency. However, most studies conducted to test the sensitivity and specificity of this procedure have been on hemodialysis patients. There is reason to believe that the response to erythropoietin therapy may differ in peritoneal dialysis patients. A recent study was conducted to determine predictive values of several iron-status indices in the diagnosis of iron-deficiency anemia in peritoneal dialysis patients.

This open, prospective study was conducted on 21 stable anemic CAPD patients who were receiving erythropoietin and oral iron supplementation for more than three months. All patients were treated with 1000 mg of intravenous ferric saccharate infusion. Patients who responded to the iron infusion within three months by increasing serum hemoglobin by greater than 1 mg/dL were defined as being functionally iron deficient at baseline. Fifteen patients did respond to the iron infusion, indicating an iron deficiency. Nine of 13 patients with the presence of stainable iron still responded to the iron infusion, indicating a functional iron deficiency. Serum ferritin and transferrin saturation increased steadily after intravenous iron therapy and started to decline at the end of the study.

All available studies, including this current study, have-suggested that intravenous iron supplementation is superior to oral supplementation. None of the iron-status indices in this study were found to be reliable for the diagnosis of iron deficiency in peritoneal dialysis patients, including serum ferritin, transferrin saturation, bone marrowstainable iron, and reticulocyte hemoglobin content. No single value of iron-status indices can definitely exclude iron-deficiency anemia in peritoneal dialysis patients. Before iron-deficiency anemia is ruled out, one should be certain that hemoglobin concentrations do not increase after intravenous iron administration.

Somnuek Domrongkitchaiporn, Boonchai Jirakranont, Kalayanee Atamasrikul, et al., Indices of Iron Status in Continuous Ambulatory Peritoneal Dialysis Patients, Am J Kidney Diseases 34(1): 29-35 (July 1999) [Correspondence: Somnuek Domromgkitchaiporn, MD, Dept. of Medicine, Ramathibodi Hospital, Rama 6, Bangkok 10400. Thailand. E-mail: rasdr@mahidol.ac.th.]