[1] Toensberg Cty Hosp, Dept Med, Renal Sect, N-3103 Tonsberg, Norway
[2] Univ Oslo, Ullevaal Hosp, Dept Prevent Med, N-0407 Oslo, Norway
[3] Univ Oslo, Ullevaal Hosp, Clin Res Ctr, N-0407 Oslo, Norway
[4] Synlab Med Versorgungzentrum Labordiagnost Heidel, Heidelberg, Germany
[5] Med Univ Graz, Inst Clin Med, Graz, Austria
[6] Med Univ Graz, Chem Lab Diagnosis, Graz, Austria
[7] Univ Uppsala Hosp, Renal Unit, Dept Med Sci, Uppsala, Sweden
[8] Western Infirm Hosp, Dept Med & Therapeut, Glasgow, Lanark, Scotland
[9] Univ Toronto, Univ Hlth Network, Toronto, ON M5S 1A1, Canada
[10] Heilig Hartziekenhuis, Dept Med, Roeselare, Belgium
[11] Univ Klinikum Charite, Berlin, Germany
[12] Helsinki Univ Hosp, Helsinki, Finland
[13] Univ Zurich Hosp, CH-8091 Zurich, Switzerland
[14] Univ Oslo, Hosp Rikhosp, Dept Med, Oslo, Norway