Footnotes

• Contributors PP has conceived, written the first draft, re-edited, finally approved and submitted the manuscript. SR has read and edited the first draft, added further arguments, re-read and finally approved the manuscript.

• 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 None declared.

• Patient consent Not required.

• Provenance and peer review Commissioned; internally peer reviewed.