Funding for this research was provided by:
Uniwersytet Medyczny im. Piastów Slaskich we Wroclawiu (ST-B010.16.044)
Received: 8 March 2020
Accepted: 15 July 2020
First Online: 29 July 2020
Ethics approval and consent to participate
: The study protocol was approved by the Bioethics Committee of Wroclaw Medical University (permission no. KB–343/2016) in accordance with the Declaration of Helsinki. Participation in the study was voluntary and anonymous, and the collected data was treated confidentially. Written informed consent was obtained from a parent or guardian for participants under 16 years old.
: Not applicable.
: The authors declare that they have no competing interests related to this study.