Article History
Received: 24 December 2018
Accepted: 3 June 2019
First Online: 11 July 2019
Ethics approval and consent to participate
: Ethics approval for this study was granted by the Human Research Ethics Committee (HREC) of the University of the Witwatersrand. This was a retrospective study, the need for consent to participate was waived.
: Not applicable.
: The authors declare that they have no competing interests.