Article History
Received: 3 October 2017
Accepted: 1 June 2018
First Online: 9 June 2018
Compliance with ethical standards
: The study was conducted in accordance with the ethical standards laid down by the Declaration of Helsinki [CitationRef removed]. Approval for the study was granted by the University of Pretoria, Faculty of Health Sciences (Ethics reference number: 263/2015).
: The authors declare that they have no conflict of interest.