[1] Univ Kentucky, Med Ctr, Div Nephrol Bone & Mineral Metab, Lexington, KY 40536 USA
[2] Hosp Santa Cruz, Dept Nephrol, Lisbon, Portugal
[3] Univ Kentucky, Dept Biostat Stat & Epidemiol, Lexington, KY 40536 USA
[4] Curry Cabral Hosp, Dept Nephrol, Lisbon, Portugal
[5] Univ Porto, Hosp S Joao, Dept Nephrol, Sch Med, P-4100 Oporto, Portugal
[6] Univ Porto, Nephrol Res & Dev Unit, P-4100 Oporto, Portugal
[7] Sch Business, ISCTE, Lisbon, Portugal