Received: 29 January 2018
Accepted: 21 May 2018
First Online: 31 May 2018
Ethics approval and consent to participate
: The need for ethical approval was waived by the Ethical Review Board of the Medical Association of Saxony-Anhalt, Halle, Germany, (project ID 75/17) and by the Ethical Review Board of the Medical Association of Saxony, Dresden, Germany (project ID EK-BR-15/12–1). Consent to participate was not applicable due to the retrospective nature of the study.
: The need for informed consent was waived by the Ethical Review Boards of both study centers.
: The authors declare that they have no competing interests.
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