[1] Goethe Univ Frankfurt, Childrens Hosp, Dept Pediat Pulmonol Allergy & Cyst Fibrosis, D-60590 Frankfurt, Germany
[2] Univ Hosp Mainz, Dept Pulm, Mainz, Germany
[3] Goethe Univ Frankfurt, Inst Biostat & Math Modeling, D-60590 Frankfurt, Germany
[4] Goethe Univ Frankfurt, Dept Internal Med 3, D-60590 Frankfurt, Germany
[5] Univ Bonn, Childrens Hosp, Med Ctr, D-5300 Bonn, Germany