Footnotes

• Handling editor Josef S Smolen

• Contributors All authors contributed significantly to the idea, collection and analysis of data, preparation of the manuscript and all authors accepted the final version of the 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 KC: has received consultant fees from AbbVie, Pfizer, Lilly. ES: none. PPS: has received fees from grants deposited to the Special Account for Research Funding (ELKE) of the National and Kapodistrian University of Athens Medical School from AbbVie, Pfizer, MSD, Roche, UCB, GSK, Novartis. MGT: has received fees from grants deposited to the Special Account for Research Funding (ELKE) of the National and Kapodistrian University of Athens Medical School from AbbVie, MSD and Pfizer.

• Patient consent for publication Not required.

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