[1] Univ Childrens Hosp Heidelberg, Div Pediat Nephrol, Heidelberg, Germany
[2] Univ Hosp Gasthuisberg, Louvain, Belgium
[3] Univ Gothenburg, Gothenburg, Sweden
[4] Univ Budapest, Budapest, Hungary
[5] Prague Agr Univ, Prague, Czech Republic
[6] IRCCS, Osped Bambino Gesu, Rome, Italy
[7] Univ Gottingen, Gottingen, Germany
[8] Univ Gottingen, Dept Clin Chem, Gottingen, Germany