[1] Great Ormond St Hosp Sick Children, Dept Paediat & Neonatal Intens Care, London WC1N 3JH, England
[2] UCL, Inst Child Hlth, London WC1N 3JH, England
[3] Univ Hosp Saarland, Dept Pediat & Neonatal Intens Care Med, D-66421 Homburg, Germany
[4] Qualitatsburo Saarlandes, Saarbrucken, Germany
[5] Univ Hosp Saarland, Sch Med, D-66421 Homburg, Germany
[6] Inst Med Biometry Epidemiol & Med Informat, Homburg, Germany