[1] Fundacio Puigvert, Serv Nefrol, Barcelona 08025, Spain
[2] Univ Autonoma Madrid, Fdn Jimenez Diaz, Serv Nefrol, E-28049 Madrid, Spain
[3] Hosp Arnau Vilanova, Serv Nefrol, Lerida, Spain
[4] Hosp Univ 12 Octubre, Serv Nefrol, Madrid, Spain
[5] Hosp Virgen Camino, Serv Nefrol, Pamplona, Spain
[6] Hosp Clin Barcelona, Serv Nefrol, Barcelona, Spain
[7] Hosp Univ Bellvitge, Serv Nefrol, Barcelona, Spain