Text and Data Mining valid from 2019-03-30
Received: 17 October 2018
Accepted: 20 March 2019
First Online: 30 March 2019
Compliance with ethical standards
: The authors of this manuscript have no conflicts of interest to disclose.
: The study was approved by the institutional review board according to the general guidelines provided by the regional ethics committee (2015/1442). For this type of study formal consent is not required (retrospective study).
: 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 1964 Helsinki declaration and its later amendments or comparable ethical standards.