Footnotes

• FVM and SGGT contributed equally.

• Contributors Acquisition and interpretation of data: FVM, SGGT, AB, GP, DE, LF, EV, PB, FA and SD. Drafting of the manuscript: FVM, SGGT and AB. Critical revision of the manuscript: SD. Final approval: FVM, SGGT, AB, GP, DE, LF, EV, PB, FA, SD.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests SD has served as a speaker, consultant, and advisory board member for Schering-Plough, AbbVie, Actelion, Alphawasserman, AstraZeneca, Cellerix, Cosmo Pharmaceuticals, Ferring, Genentech, Grunenthal, Johnson and Johnson, Millenium Takeda, MSD, Nikkiso Europe GmbH, Novo Nordisk, Nycomed, Pfizer, Pharmacosmos, UCB Pharma and Vifor.

• Provenance and peer review Not commissioned; internally peer reviewed.