Indole 3-acetic acid, indoxyl sulfate and paracresyl-sulfate do not influence anemia parameters in hemodialysis patients

Background: The main reason for anemia in renal failure patients is the insufficient erythropoietin production by the kidneys. Beside erythropoietin deficiency, in vitro studies have incriminated uremic toxins in the pathophysiology of anemia but clinical data are sparse. In order to assess if indole 3-acetic acid IAA), indoxyl sulfate IS), and paracresyl sulfate PCS) -three protein bound uremic toxins-are clinically implicated in end-stage renal disease anemia we studied the correlation between IAA, IS and PCS plasmatic concentrations with hemoglobin and Erythropoietin Stimulating Agents ESA) use in hemodialysis patients. Methods: Between June and July 2014, we conducted an observational cross sectional study in two hemodialysis center. Three statistical approaches were conducted. First, we compared patients treated with ESA and those not treated. Second, we performed linear regression models between IAA, IS, and PCS plasma concentrations and hemoglobin, the ESA dose over hemoglobin ratio ESA/Hemoglobin) or the ESA resistance index ERI). Third, we used a polytomous logistic regression model to compare groups of patients with no/low/high ESA dose and low/high hemoglobin statuses. Results: Overall, 240 patients were included in the study. Mean age +/- SD was 67.6 +/- 16.0 years, 55.4% were men and 42.5% had diabetes mellitus. When compared with ESA treated patients, patients with no ESA had higher hemoglobin mean 11.4 +/- 1.1 versus 10.6 +/- 1.2 g/dL; p < 0.001), higher transferrin saturation TSAT, 31.1 +/- 16.3% versus 23.1 +/- 11.5%; p < 0.001), less frequently an IV iron prescription (52.1 versus 65.7%, p = 0.04) and were more frequently treated with hemodiafiltration (53.5 versus 36.7%). In univariate analysis, IAA, IS or PCS plasma concentrations did not differ between the two groups. In the linear model, IAA plasma concentration was not associated with hemoglobin, but was negatively associated with ESA/Hb (p = 0.02; R = 0.18) and with the ERI p = 0.03; R = 0.17). IS was associated with none of the three anemia parameters. PCS was positively associated with hemoglobin (p = 0.03; R = 0.14), but negatively with ESA/Hb (p = 0.03; R = 0.17) and the ERI (p = 0.02; R = 0.19). In multivariate analysis, the association of IAA concentration with ESA/ Hb or ERI was not statistically significant, neither was the association of PCS with ESA/ Hb or ERI. Identically, in the subgroup of 76 patients with no inflammation CRP <5 mg/L) and no iron deficiency TSAT >20%) linear regression between IAA, IS or PCS and any anemia parameter did not reach significance. In the third model, univariate analysis showed no intergroup significant differences for IAA and IS. Regarding PCS, the Low Hb/High ESA group had lower concentrations. However, when we compared PCS with the other significant characteristics of the five groups to the Low Hb/high ESA (our reference group), the polytomous logistic regression model didn't show any significant difference for PCS. Conclusions: In our study, using three different statistical models, we were unable to show any correlation between IAA, IS and PCS plasmatic concentrations and any anemia parameter in hemodialysis patients. Indolic uremic toxins and PCS have no or a very low effect on anemia parameters.