Received: 13 August 2019
Accepted: 6 December 2019
First Online: 18 December 2019
Ethics approval and consent to participate
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the principles of the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. The present study was retrospective; for this type of study, the local ethics committee waived formal consent.
: Not applicable.
: The authors declare that they have no competing interests.