Funding for this research was provided by:
Warszawski Uniwersytet Medyczny ((FW113/NM1/17, FW113/NM2/13, FW113/NM1/14, FW113/PM32/14))
Text and Data Mining valid from 2018-05-29
Received: 12 September 2017
Accepted: 11 May 2018
First Online: 29 May 2018
Ethics approval and consent to participate
: This study was approved by the Institutional Bioethics Committees (KB/127/2012 and KB/67/2017 at the Medical University of Warsaw; 7/PB/2015 at the Medical Centre of Postgraduate Education). Before data collection, study objectives were explained to patients and their written informed consent was obtained.
: The authors declare they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.