[1] Univ Renal Res & Educ Assoc, Ann Arbor, MI 48103 USA
[2] A Manzoni Hosp, Dept Nephrol & Dialysis, Lecce, Italy
[3] Hop St Andre, Nephrol & Hemodialysis Serv, Bordeaux, France
[4] Heidelberg Univ, Nephrol Sect, Heidelberg, Germany
[5] Univ Naples Federico II, Dept Nephrol, Naples, Italy
[6] Hosp Gen Valle Hebron, Serv Nephrol, Barcelona, Spain
[7] Lister Hosp, Dept Renal Med, Stevenage, Herts, England
[8] Univ Penn, Sch Med, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA