Footnotes

• Contributors YF, HG, LDU and RDDS planned and wrote the article. YF, HG, LDU, RDDS, AK and CL contributed in the writing and editing of the manuscript. All authors read and 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 for publication Not required.

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