Footnotes

• Contributors ES: data collection, data interpretation, literature search, figures and writing. GSB: writing. RPHP: data interpretation, literature search and writing. ES and RPHP had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. ES and RPHP are responsible for data analysis.

• Competing interests None.

• Patient consent Obtained.

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