Received: 25 November 2017
Accepted: 4 April 2018
First Online: 13 April 2018
Ethics approval and consent to participate
: This study was carried out in accordance with the recommendations of the Ethics Committee of the Medical Faculty of the Leipzig University (approvals no. 148–2005, 159–12-21,052,012, 017–12-23,012,012). All subjects gave written informed consent in accordance with the Declaration of Helsinki.
: The authors declare that they have no competing interests.
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