Footnotes

• Contributors All the authors had carefully read the manuscript of Memtsoudis et al and analyzed their methods and data. YC suggested comment points and drafted this manuscript. FSX critically revised comment points and this manuscript and is the author responsible for this paper. SHL revised comment points and this paper. 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.

• Patient consent for publication Not required.

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