Received: 26 February 2020
Accepted: 5 May 2020
First Online: 20 May 2020
Ethics approval and consent to participate
: Waiver of informed consent for the retrospective analysis of the clinical sample was obtained from the ethics review board of the general medical council of the state of Hamburg, Germany. All procedures performed in this study were in accordance with the ethical standards of the ethics review board of the general medical council of the state of Hamburg, Germany, and with the 1964 Helsinki declaration and its later amendments.
: There is no actual or potential conflict of interest for any of the authors.
: The authors declare that they have no competing interests.