1. MVZ DaVita Dormagen GmbH, Diabetes and Renal Center, Dormagen, Germany
2. Internal Medicine, Catholic Clinics Oberberg, St. Josef Hospital, Engelskirchen, Germany
3. University Hospital Leipzig, Department of Endocrinology, Nephrology and Rheumatology, Leipzig, Germany
4. Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Renal Medicine, Stockholm, Schweden, Germany
5. Medical Clinic IV, Diabetology, Endocrinology, Nephrology, University Hospital Tübingen, Germany
6. Institute for Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics, University Hospital Leipzig, Germany