Received: 28 September 2018
Accepted: 25 March 2019
First Online: 1 April 2019
Ethics approval and consent to participate
: Ethical approval for this retrospective observational study was obtained from the Medical Ethics Committee of Leiden University, the Netherlands (p11.184).
: Not applicable.
: The authors declare that there are no conflicts of interest according to the guidelines of the International Committee of Medical Journal Editors.