Footnotes

• Contributors CCR, TMAvH, SBH and ABtP conceived the concept of the study. TMAvH performed the data acquisition, input and analysis with help from SZ for the data analysis. The manuscript draft was written by TMAvH; CCR, JD, SBH and ABtP contributed to the completion of 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.

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

• Patient consent for publication Not required.