title: The authors reply.
authors: Pediatric Pulmonology, Erasmus MC-Sophia Children's Hospital, Rotterdam, The Netherlands.
authors: Marije
authors: M
authors: Bakker
authors: Gerard
authors: G
authors: Borsboom
authors: Harm
authors: H
authors: Tiddens
mesh_terms: D003550:Cystic Fibrosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D013147:Spirometry