Abstract
Serum erythropoietin (Epo) levels are influenced by the integrity of renal function, the severity and etiology of anemia, the percentage of hemoglobin F and other factors. We aimed to create a parametric expression for the response to anemic/hypoxic stress and we evaluated serum Epo levels in 1096 subjects with normal renal function, of whom 837 were anemic (Hb 16.5 g/dl). Hb ranged between 3.6 and 23.8 g/dl and the corresponding Epo between <3.4 and 2670 mIU/ml. Between log-Epo and Hb the correlation co-efficient r was ?0.706. The function linking Hb and log-Epo was determined as log(Epo) = 3.05 - 0.131 × Hb. Investigating various mathematic models, which could parametrically express the “response to anemia/hypoxia”, we found that the Hb × log(Epo) product was a stable parameter and fitted a normal distribution. Arbitrarily defining as normal range about one SD between the mean (12 - 21) we found that only 224 patients (20.8%) exhibited a Response to Anemia Index (RAI) beyond these limits. Below the lower limit there were 106 patients, diagnosed with polycythemia vera (12/38, 31.6%) anemia of chronic disease (10/34, 29.4%), megaloblastic anemia (17/56, 30.4%) and β-thalassemia trait (11/41, 26.8%). Forty-eight patients (45.3%) were diabetic. Above the defined upper normal RAI limit there were 118 patients, mainly diagnosed with secondary erythrocytosis (24/34, 70.6%), aplastic anemia (8/20, 40%), hemolytic anemia (3/14, 21.4%) and myelodysplastic syndromes (46/326, 14.1%). RAI was a rather constant parameter for each individual, with minimal variation in different evaluations, when Epo was estimated in the absence of inflammatory conditions. We have validated the superiority of RAI for the prediction of response to Epo in a cohort of 669 patients, who received Epo treatment. It is concluded that RAI is a reliable parameter describing the response to hypoxic/anemic stress.
Highlights
Under normal renal function, for any hemoglobin (Hb) value, there is a short range of corresponding circulating serum erythropoietin (Epo) levels, and these two parameters are inversely associated [1]
We aimed to create a parametric expression for the response to anemic/hypoxic stress and we evaluated serum Epo levels in 1096 subjects with normal renal function, of whom 837 were anemic (Hb < 12 g/dl), 204 were non anemic (Hb 12 - 16.5 g/dl), and 55 were erythremic (Hb > 16.5 g/dl)
Investigating various mathematic models, which could parametrically express the “response to anemia/hypoxia”, we found that the Hb × log(Epo) product was a stable parameter and fitted a normal distribution
Summary
For any hemoglobin (Hb) value, there is a short range of corresponding circulating serum erythropoietin (Epo) levels, and these two parameters are inversely associated [1]. Serum Epo levels reflect the individual’s response to hypoxic/anemic stress. This response is determined by various factors, such as the adequacy of renal and liver function [2], the etiology, severity and probably the chronicity of the anemia, the presence and percentage of HbF [3] [4], the circulation of inflammatory cytokines antagonizing erythropoietin [5], the percentage of bone marrow red blood cell precursors, the metabolic rate of Epo, the presence of diabetes mellitus [6] [7], and plasma viscosity. Serum Epo levels, in the absence of inflammation, renal and hepatic failure, are mainly determined by the etiology and the severity of the anemia, i.e. by the corresponding Hb levels
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