Assessment of erythropoiesis activity during hemodialysis therapy by soluble transferrin receptor levels and ferrokinetic measurements

Abstract

The Erythropoietic Activity (EA) and degree of erythropoiesis attained by patients undergoing hemodialysis (HD) administered recombinant human erythropoietin (rHuEPO) were studied using ferrokinetic measurements and tests of soluble transferrin receptor (sTfR) levels, assessing which parameter is most useful for measurements in clinical practice. Plasma iron 59 (59Fe) clearance (half-life [T1/2 ] 59Fe), plasma iron turnover (PIT), erythron transferrin uptake (ETU), and erythrocyte 59Fe incorporation were determined in 23 patients before and at 4 months after administration of rHuEPO. sTfR levels, hematopoietic parameters, and iron metabolism parameters were measured periodically. T1/259Fe was shortened (P = 0.004), PIT and ETU were increased (P = 0.032 and P = 0.013, respectively), and the time taken by erythrocytes to incorporate 80% of the 59Fe administered was reduced from 9.6 to 6.1 days. sTfR levels were increased by 15 days; this increase was significant (P < 0.05) at 30 days, reaching a maximum of 3.22 mg/dL at day 45. A positive correlation was seen between sTfR levels and hemoglobin (Hb) (P = 0.001), hematocrit (P = 0.001), and reticulocytes (P = 0.038) that was not found between ferrokinetic parameters and those evaluating efficient erythropoiesis (P = 0.345 between ETU and Hb). In conclusion, EA is increased, shown by ETU and sTfR level. sTfR levels correlate with the parameters that evaluate efficient erythropoiesis, and their measurement does not involve the technical and/or ethical limitations of studies of ferrokinetics, making them the tool of choice in clinical practice for the evaluation of EA in patients undergoing HD administered rHuEPO.