Text and Data Mining valid from 2019-10-03
Received: 9 September 2019
Accepted: 23 September 2019
First Online: 3 October 2019
Compliance with ethical standards
: All the procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.This is a systematic review on retrospective studies which were conducted on already available data for which formal consent was obtained. Therefore, institutional ethical approval is not required according on the law and the national ethical guidelines.
: Informed consent was not obtained from individual participants due the fact that this review included retrospective studies for which formal consent was obtained.