Received: 17 July 2018
Accepted: 9 October 2018
First Online: 26 October 2018
Ethics approval and consent to participate
: The study and its consent procedure were approved by the Bioethics Committee (133/KBE/2014) of the Children’s Memorial Health Institute in Warsaw. All study subjects gave informed, written consent prior to their participation; consent on behalf of all children taking part was given in writing by their parents or guardians.
: The study was conducted in compliance with Polish law and the General Data Protection Regulation (GDPR) (EU) 2016/679.Written consent was obtained for use of all patient data.
: The authors declare that they have no competing interests.
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