Footnotes

• Contributors All authors made substantial contributions to the design and conception of this study, the interpretation of the data and revised the manuscript critically for important intellectual content. BEAS drafted the manuscript. BEAS and BM analysed the data. BEAS, SH and VAC were involved in the acquisition of the data.

• Funding This work solely used institutional funds and was not funded by third parties.

• Competing interests None declared.

• Patient consent Obtained.

• Ethics approval This study complies with the Declaration of Helsinki and was approved by the institutional ethics committee of the medical faculty of the University of Bonn.

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