1. Department of Nephrology, DaVita, Lisbon, Portugal
2. Department of Nephrology, DaVita International, Krakow, Poland
3. Department of Nephrology, DaVita, Porto, Portugal
4. Department of Nephrology, DaVita, Riyadh, Saudi Arabia
5. DaVita International, Washington DC, USA
6. Department of Nephrology, DaVita, Dusseldorf, Germany
7. Department of Nephrology, DaVita, Bialystok, Poland
8. Unit for Medical Statistics, Department of Clinical Sciences, Karolinska Institutet, Danderyd University Hospital, Stockholm, Sweden
9. Division of Nephrology, Department of Clinical Sciences, Karolinska Institutet, Danderyd University Hospital, Stockholm, Sweden