Received: 3 August 2019
Accepted: 8 June 2020
First Online: 17 June 2020
Ethics approval and consent to participate
: Ethics approval for this study was obtained from the Domain-Specific Review Board of the National Healthcare Group (NHG DSRB No: 2017/00347). This was a retrospective study using anonymised data and informed consent was not required.
: Not applicable.
: The authors declare that they have no competing interests.