Accepted: 6 March 2018
First Online: 9 March 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: 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.
: Informed consent was waived by the institutional review board of the Academic Medical Centre Amsterdam. For reason of the audit design of the study.