[1] Humboldt Univ, Fak Med, Univ Klinikum Charite, Dept Nephrol & Med Intens Care, D-13353 Berlin, Germany
[2] Univ St Cyril & Methudius, Dept Nephrol, Skopje 91000, Macedonia
[3] Med Univ Gdansk, Dept Nephrol, Gdansk, Poland
[4] Univ Gottingen, Dept Nephrol & Rheumatol, D-3400 Gottingen, Germany
[5] Membrana GmbH, Wuppertal, Germany
[6] Univ Ulm, Dept Biometry & Med Documentat, Ulm, Germany