1. Nephrology Section, Príncipe de Asturias University Hospital, Alcalá de Henares, Madrid - Spain
2. Research Unit of the Foundation for Biomedical Research, Príncipe de Asturias University Hospital, Alcalá de Henares, Madrid - Spain
3. Nephrology Section, Infanta Leonor Hospital, Vallecas, Madrid - Spain
4. Nephrology Section, Hospital of Segovia, Segovia - Spain
5. Nephrology Section, Río Carrión Hospital, Palencia - Spain
6. Nephrology Section, Virgen de la Concha Hospital, Zamora - Spain
7. Ponfedial Dialysis Center, Ponferrada, León - Spain
8. Nephrology Section, Soria Hospital, Soria - Spain