The purpose of this study es to determine hemoglobin variability in kidney transplant recipients with chronic renal anemia.

The primary endpoint of the study is hemoglobin level variability. For determination of this variability, the following patterns of hemoglobin level change will be established:

• Target range hemoglobin (TRH): patients with hemoglobin values in the range of 11.0-12.0g/dl throughout the study period.
• Low hemoglobin (LH): patients with levels below 11.0g/dl
• High hemoglobin (HH): patients with levels above 12.0g/dl
• Low-amplitude fluctuation with low hemoglobin (LALH): patients with at least one measurement of hemoglobin levels <11.0g/dl and at least one measurement in the range of 11.0-12.0g/dl, but without hemoglobin measurements >12.0g/dl.
• Low-amplitude fluctuation with high hemoglobin (LAHH): patients with at least one measurement of hemoglobin levels >12.0g/dl and at least one measurement in the range of 11.0-12.0g/dl, but without hemoglobin measurements <11.0g/dl.
• High-amplitude fluctuation (HAH): patients with at least one measurement of hemoglobin levels <11.0g/dl and at least one measurement >12.0g/dl.

Secondary objectives:

• To determine potential factors influencing hemoglobin variability.
• To assess the influence of hemoglobin variability on cardiovascular risk of patients according to the REGICOR function at the end of the study period.

Inclusion Criteria:

• Patients aged > or = 18 years.
• Kidney transplant recipients with chronic renal failure stage 3 (glomerular filtration rate: 30-59ml/min/1.73m2), 4 (glomerular filtration rate: 15-29ml/min/1.73m2) or 5 (glomerular filtration rate: <15ml/min/1.73m2) at the start of the study follow-up period.
• Diagnosis of anemia and drug treatment initiated or changed subsequent to June 29, 2010 (date on which the latest recommendation by European Renal Best Practice on the target range for hemoglobin levels were published)
• Patients capable of giving their informed consent to participate in the study and who agree to participate by signing the informed consent form.

Exclusion Criteria:

• Patients whose medical history lacks measurements of hemoglobin levels every three months (±1 month) during the year of study follow-up.

Adult kidney transplant recipients with chronic renal anemia.