Footnotes

• Handling editor Josef S Smolen

• Contributors GAR, MG, TS, RC and LD designed the study. All authors contributed to data collection. GAR, MG, TS and LMA analysed the data. GAR drafted the manuscript. All authors contributed to the design of the study and to revise it critically for important intellectual content. All authors contributed to revising the manuscript and approved its final version.

• 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 and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

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