Footnotes

• Contributors Substantial contributions to the conception or design of the work: acquisition, analysis and interpretation of data: AT, MPr, MPi, FG, CDI, DP, EI; drafting the work or revising it critically for important intellectual content: AT, MPi, EI; final approval of the version published, agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved: AT, MPr, MPi, FG, CDI, DP, EI.

• Competing interests None declared.

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