This is an observational clinical research on patients with chronic kidney disease who are not on hemodialysis and receiving darbepoetin alfa to treat diagnosed renal anemia; the major objective is to explore novel erythropoiesis stimulating agent (ESA) response index in association with deterioration of renal function as well as occurrence of cardiovascular disease events.

Inclusion Criteria:

1. Patients who are planning to start treatment with darbepoetin alfa within 8 weeks after enrollment,
2. Patients with eGFR <60 mL/min/1.73m2 at the latest examination performed within 8 weeks before enrollment,
3. Patients with a hemoglobin level <11.0 g/dL at the latest examination performed within 8 weeks before enrollment,
4. Patients aged at least 20 years or older at the time of providing informed consent,
5. Patients who voluntarily provided written informed consent to participate in the study.

Exclusion Criteria:

1. Patients who are planning to start hemodialysis or to have a renal transplant within 24 weeks after enrollment,
2. Patients with a history of treatment with ESA except the ones who were treated temporarily more than 12 weeks before the enrollment,
3. Patients with malignant tumor, hematological disease, or hemorrhagic lesions,
4. Patients with hypersensitivity to ESA or any ingredient thereof,
5. Pregnant, lactating or possibly pregnant women or those who wish to become pregnant during the study period,
6. Patients who are participating in other clinical study,
7. Patients who are assessed as not eligible for the study by the investigator.

Chronic renal disease patients without dialysis who are diagnosed with renal anemia and are administered darbepoetin alfa at enrollment