1. Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
2. Laboratory of Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
3. Department of Internal Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
4. Department of Laboratory Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
5. Certe Medical Diagnostics and Advice, Medical Center Leeuwarden, Leeuwarden, The Netherlands