In addition to High vs. Low sEpoR levels, we adjusted for characteristics previously linked with erythropoietin administration including age, race, sex, cause of end-stage renal failure (diabetes, hypertension, glomerulonephritis, other), and baseline exposures such as arterio-venous access (fistula, graft, catheter), weight, serum ferritin, transferrin saturation, and PTH levels [42]–[44]. This evidence concerns the gene PTH and stage 5 chronic kidney disease.