1. Department of Nephrology, Hospital Central Defense Gomez Ulla, 28047 Madrid, Spain
2. Department of Nephrology, Guadalajara Center Dialysis, AVERICUM, 19003 Guadalajara, Spain
3. Department of Nephrology, Clinica Universidad de Navarra, 28027 Madrid, Spain
4. Department of Nephrology, Hospital Universitario General Villalba, 28400 Madrid, Spain
5. Department of Anatomic Pathology, Hospital Gregorio Marañón, 28008 Madrid, Spain