Footnotes

• Handling editor Josef S Smolen

• Twitter @KruscheMartin, @SandraKurkowski, @ina_kotter, @JK77775

• Contributors FM, JK, JM, IK, MK, SK participated in the conception of the study and data interpretation and drafted the manuscript. All authors participated actively in the discussions and had a prior methodological training. All gave substantial intellectual contributions, and read, revised 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 and public involvement Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods section for further details.