Funding for this research was provided by:
Deutsche Forschungsgemeinschaft (PE 2309/2-1, ER 155/6-1, ER 155/6-2)
Received: 17 October 2019
Accepted: 18 March 2020
First Online: 27 March 2020
Ethics approval and consent to participate
: The study was approved by the ethical committee at the University Hospital of Essen, Germany and was conducted in accordance with the principles expressed in the Declaration of Helsinki. The study was certified and recertified according to DIN EN ISO 9001:2000/2008. All study participants gave their written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.