1. Department of Surgical and Perioperative Sciences, Surgery, Umeå University, Umeå, Sweden
2. Department of Surgery, Grey’s Hospital, University of KwaZulu-Natal, Pietermaritzburg, South Africa
3. Department of Surgery, University of the Witwatersrand, Johannesburg, South Africa
4. Department of Statistics, Umeå School of Business, Economics and Statistics, Umeå University, Umeå, Sweden.