Footnotes

• Handling editor Tahir S Pillay.

• Contributors MJ and LW contributed to the conception and design of the study. MJ collected, analysed the data and drafted the manuscript. LW critically reviewed the manuscript.

• Funding MJ is a National Institute for Health Research Academic Clinical Fellow. The funding bodies had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; nor the decision to submit the manuscript for publication.

• Competing interests None declared.

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