This is a prospective (observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group), observational (clinical study in which participants may receive diagnostic, therapeutic, or other types of interventions, but the investigator does not assign participants to specific interventions) and cohort study. Study specific information will be collected from participants with chronic renal disease who are receiving recombinant erythropoietin and their treatment course will be followed for up to 2 years and participants will not receive any intervention in this study. Upon entering the study, information will be collected regarding disease history and recombinant erythropoietin treatment. Every 3 months thereafter, progress information will be collected, including recombinant erythropoietin treatment, number of red blood cells and presence of any signs of pure red cell aplasia (PRCA) development. Blood samples will be collected at study entry and every 3 months. Participants discontinuing erythropoietin will be followed only for an additional 12 months from the time erythropoietin is discontinued. Participants will receive standard-of-care treatment for their chronic renal disease from their individual Investigators. Participants will be primarily observed prospectively for PRCA.
