Received: 14 November 2017
Accepted: 3 April 2018
First Online: 20 April 2018
Compliance with ethical standards
: All authors declare that they have no conflicts of interest and that they have no competing interests in relation to this manuscript.
: All procedures were approved by Institutional Review Board and performed in accordance with the Declaration of Helsinki of the World Medical Association.
: Considering that all subjects were less than 18 years, a consent form was received from their parents after verbal and written explanation of the experimental design of this study.