Article History
Received: 5 September 2017
Accepted: 6 August 2018
First Online: 20 August 2018
Compliance with ethical standards
: The study design was approved by the Ethics Committee of the Medical University of Silesia (Katowice, Poland). The patients’ parents or caregivers gave their informed, written consent to enrolment of their children and/or dependants into the study.
: None.