Disclosure of potential conflict of interest: M. C. Nawijn reports grant support from GlaxoSmithKline and Health Holland; unrestricted research grant on this topic; and unrestricted research grants sponsored by GlaxoSmithKline, TETRI Foundation, and Lung Foundation, SAB. H. A. M. Kerstjens received fees per patient for recruitment in trials from GlaxoSmithKline, NOVARTIS, and FLUIDDA and grants for investigator-initiated studies from GlaxoSmithKline, NOVARTIS, and Boerhinger. In addition, his institution has through his work received consultancy fees from Novartis, AstraZeneca, Boehringer Ingelheim, and GlaxoSmithKline. G. H. Koppelman received grant support from the Lung Foundation of the Netherlands, TETRI Foundation, TEVA the Netherlands, UBBO EMMIUS Foundation, Vertex, and GlaxoSmithKline (money to institution). M. van den Berge had grants paid to university from GlaxoSmithKline, Chiesi, Teva, AstraZeneca, and Genentech. The rest of the authors declare that they have no relevant conflicts of interest.