PERCENTAGE OF HYPOCHROMIC RED-BLOOD-CELLS AS PREDICTOR OF ERYTHROPOIETIC AND IRON RESPONSE AFTER IV IRON SUPPLEMENTATION IN MAINTENANCE HEMODIALYSIS-PATIENTS

Background. The percentage of hypochromic red blood cells (RBC), defin ed as those with a cellular haemoglobin <28 g/dl has been suggested to be a sensitive marker of functional iron deficiency in maintenance ha emodialysis (HD) patients. Thus, during rHuEpo therapy an increase in hypochromic RBC to >10% would indicate that more intensive iron supple mentation may be required. Methods. We investigated 70 HD patients 57. 1+/-15.3 years old and on maintenance HD for 66.3+/-47.9 months withou t blood loss from gastrointestinal bleeding or from the vascular acces s, without surgery and without infectious disease or malignancy. Durin g the study period of 12 weeks, each patient received an i.v. dose of 800 mg ferrogluconate. Haemoglobin, haematocrit, and the percentage of hypochromic RBC were measured before and every 4 weeks after the star t of the study; serum ferritin, zinc protoporphyrin (ZPP) and C-reacti ve protein (CRP) were measured at the beginning (baseline) and end of the study. Results. At baseline the percentage of hypochromic RBC was less than or equal to 5.0% in 28 patients, >5.0 and less than or equal to 10.0% in 25 patients and >10.0% in 17 patients, suggesting functio nal iron deficiency in at least 42 patients. Nine patients had serum f erritin values <100 mu g/l; nonetheless in these patients the median p ercentage of hypochromic RBC was 5.9% (range 0.9-14.3%), indicating th at an absolute iron deficiency can occur in the presence of normal amo unts of hypochromic RBC. There was a significant correlation between s erum ferritin levels and hypochromic RBC at the end, but not at the be ginning, of the study. However, there was no correlation between ZPP a nd hypochromic RBC at any time during the study. During i.v. iron supp lementation the rHuEpo dose could be reduced by 8.5% in patients with hypochromic RBC less than or equal to 5.0%, by 11.3% in patients with hypochromic RBC >5.0 and less than or equal to 10.0% and by 23.4% in p atients with hypochromic RBC >10.0%, demonstrating the benefit of i.v. iron in patients with functional iron deficiency. In HD patients in w hom serum ferritin levels remained below 290 mu g/l until the end of t he study, a significant reduction of the rHuEpo dosage could be obtain ed during i.v. iron therapy. This was not the case in patients with se rum ferritin >290 mu g/l after iron supplementation. We found that the percentage of hypochromic RBC is the most sensitive parameter for pre dicting hyporesponsiveness in CRP-positive patients. HD patients with hypochromic RBC >6% and low to moderate increases in serum ferritin le vels after i.v. iron supplementation significantly benefit from i.v. i ron therapy compared to HD patients with hypochromic RBC <6%. Conclusi ons. Two different aspects should be taken into consideration in I-ID patients treated with rHuEpo and concomitant i.v. iron therapy: (1) re sponse of the erythropoietic system to rHuEpo, and (2) adequate delive ry of the supplemented iron to the erythropoietic system. The patient' s percentage of hypochromic RBC and increase in serum ferritin after i .v. iron supplementation should be used to decide whether or not i.v. iron should be given and to monitor this type of therapy in HD patient s.