Received: 27 March 2019
Accepted: 17 July 2019
First Online: 22 July 2019
Ethics approval and consent to participate
: Written informed consent was obtained from the legal guardian of the children. The study was performed according to the guidelines of the Institutional Review Board on the use of biological specimens for scientific purposes in keeping with Italian law (art.13 D. Lgs 196/2003). Since this was a retrospective study on the results already available with us, it was not put up for any clearance to an ethical committee. The data were handled anonymously. The study accomplished the Helsinki Declaration of 1975, rev. 2000.
: Not applicable.
: No financial and non-financial competing interests are declared.