Received: 20 September 2017
Accepted: 18 January 2018
First Online: 30 January 2018
Ethics approval and consent to participate
: The study complies with the principles of the Declaration of Helsinki. The study protocol was approved by the Semmelweis University Regional and Institutional Committee of Science and Research Ethics (ETT TUKEB 52/2014).
: Not applicable – this manuscript does not contain any individual person’s data in any form (including individual details, images or videos).
: No author reported any potential conflict of interest regarding the present study.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.