Received: 10 January 2021
Accepted: 22 March 2021
First Online: 5 April 2021
: The study was approved by the institutional review board of the principal study centre (Bergamo), which collected the data from the other centres in aggregated and anonymous form. All procedures were performed in accordance with the ethical standards of the institutional committee and the tenets of the 1964 Helsinki Declaration and its later amendments.
: Not applicable.
: The authors declare that they have no competing interests.