Received: 5 November 2018
Accepted: 12 March 2019
First Online: 27 March 2019
Ethics approval and consent to participate
: The study was approved by the Ethics Committee of the University of Marburg as coordinating center and by the Ethics Committees of all study centers; it is registered on ExternalRef removed (registration number NCT01245933).
: Not applicable.
: The authors declare that they have no competing interests.
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