Data Collection and Measurements

Patients in the registry are seen at baseline and yearly thereafter. At each visit, patients undergo a physical examination, including measurement of height and weight and office and 24-hour blood pressure measurements. Office blood pressure measurements were done in the supine position after at least 5 minutes of rest using the oscillometric method. At baseline, TKV was determined by magnetic resonance imaging using the ellipsoid method and patients were subclassified according to height-adjusted TKV ranges for age into Mayo classes 1A to E.15 Standardized blood and urine analysis, including a 24-hour urine collection, are conducted at baseline and then annually. All blood analyses were performed after at least a 6-hour fast in the morning before noon. Urine and blood analyses were performed at the Central Laboratory of Bern University Hospital, Bern, Switzerland, using standard laboratory methods. The creatinine-based CKD Epidemiology Collaboration (CKD-EPI) 2009 equation was used to estimate GFR.16

Diabetes was defined as reported, treated, or fasting glycemia with glucose level ≥ 7 mmol/L. Hypertension was defined as either systolic blood pressure ≥ 140 mm Hg, diastolic blood pressure ≥ 90 mm Hg, or use of antihypertensive medications.