A time adjusted mean change in hemoglobin (Hb) concentration was calculated using an area under the curve approach, for both periods separately. Change in Hb concentration between the baseline (Week -4 to Week -1) and evaluation periods was calculated by subtracting the calculated average baseline Hb value from the average evaluation period Hb value. All blood samples for Hb measurements were taken prior to study drug administration. The analysis used the last observation carried forward (LOCF) for missing Hb values for correction of the impact of early drop outs. The baseline period was defined as Week -4 to Week -1. The evaluation period was defined as Week 29 to Week 36.

The per protocol population was all randomized and treated participants, except those who had not met criteria for stable baseline Hb,and adequate iron levels or had hemoglobinopathies/hemolysis, RBC transfusion/blood loss, <5 recorded Hb values during evaluation or missed administrations of trial drugs in week 26 to 35.

The average Hb of all values recorded during the evaluation period was calculated, and this average was subtracted from the average baseline Hb values for each participant. The number of participants maintaining their average Hb within +/- 1 g/dL of their average baseline Hb concentration is displayed. The evaluation period was defined as Week 29 to Week 36.

The Intent-to-Treat (ITT) population was defined as all randomized participants. Participants with available data at the time of evaluation were analyzed.

A combined data of the number of participants who received Red Blood Cell (RBC) transfusions during the titration and evaluation periods is reported. A period of 28 weeks after the first dose of the study drug was used for dose titration and stabilization of Hb concentration. The dose titration period was followed by an 8-week evaluation period (weeks 29 to 36).

The safety population was defined as all participants who received at least one dose of RO0503821 or darbepoetin alfa and had a safety follow-up, whether withdrawn prematurely or not.

A marked abnormality range was defined as above and/or below a value which was considered to be potentially clinically relevant. Marked laboratory abnormalities were analyzed according to the Roche specified limits for the reference range of the following laboratory parameters: White blood cells (WBC) (3.0- 18.0 10^9/liter [L]), platelets (100 - 550 10^9/L), (alanine aminotransferase [(ALAT)] (0 - 110 units per liter [U/L]), alkaline phosphatase (ALP) (0 - 220 U/L), aspartate aminotransferase (ASAT) (0 - 80 U/L), albumin >= 30 g/L, phosphate (0.75 - 1.60 millimole per liter [mmol/L]), potassium (2.9 - 5.8 mmol/L), glucose (2.80 - 11.10 mmol/L).

The safety population was defined as all participants who received at least one dose of RO0503821 or darbepoetin alfa and had a safety follow-up, whether withdrawn prematurely or not. Data from participants available at protocol specified assessment time points were included in the analysis (n).

Blood pressure Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP) was measured by manual assessment or automated reading throughout the study for every participant. Blood pressure was taken in the sitting position after at least 5 minutes rest. An appropriate -sized cuff was used and both systolic and diastolic blood pressures were recorded before dialysis (BD) and after dialysis (AD).

The safety population was defined as all participants who received at least one dose of RO0503821 or darbepoetin alfa and had a safety follow-up, whether withdrawn prematurely or not. Data from participants available at protocol specified assessment time point were included in the analysis (n).

Change in pulse rate (beats per minute [bpm]) from baseline values includes only those participants with both a baseline (BL) value and a value for specified time period.

The safety population was defined as all participants who received at least one dose of RO0503821 or darbepoetin alfa and had a safety follow-up, whether withdrawn prematurely or not. Data from participants available at protocol specified assessment time point were included in the analysis (n).

An Adverse Event (AE) is defined as any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. A Serious Adverse Event (SAE) is defined as any untoward medical occurrence that, at any dose, results in death, is life threatening, requires hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, or is a significant medical event in the investigator's judgment or requires intervention to prevent one or other of these outcomes. Overall deaths occurred in the study were reported.

The safety population was defined as all participants who received at least one dose of RO0503821 or darbepoetin alfa and had a safety follow-up, whether withdrawn prematurely or not.