Footnotes

• Contributors All authors had carefully read the manuscript of Carella et al, analyzed their methods and data. F-SX suggested comment points and drafted this manuscript and is the author responsible for this manuscript. NH and YC revised comment points and this manuscript. All authors had seen and approved the final 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; externally peer reviewed.