Received: 22 December 2017
Accepted: 30 April 2018
First Online: 10 May 2018
Ethics approval and consent to participate
: This study was conducted with the agreement of the local ethics committees of each study centre (Mainz: Ethik-Kommission der Landesärztekammer Rheinland-Pfalz: 837.082.15/9850, 2015–04-02; Würzburg: Ethik-Kommission der Bayerischen Landesärztekammer: 149/15_z, 2015–07-16). All participants gave written informed consent.
: The authors declare that they have no competing interests.
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