[1] Univ Zimbabwe, Fac Med & Hlth Sci, Internal Med Unit, Harare, Zimbabwe
[2] Levy Mwanawasa Med Univ, Sch Med & Clin Sci, Lusaka, Zambia
[3] Obafemi Awolowo Univ, Teaching Hosp Complex, Dept Surg, Div Gastrointestinal Surg Oncol, Ife, Osun, Nigeria
[4] Univ Sierra Leone, Teaching Hosp Complex Highest, Coll Med & Allied Hlth Sci, Dept Pathol, Freetown, Sierra Leone
[5] Univ Cape Town, Fac Hlth Sci, Dept Med, Rondebosch, Western Cape, South Africa
[6] Queen Mary Univ London, Blizard Inst, Barts & London Sch Med & Dent, London, England
[7] Univ Cape Town, Anzio Rd,Observ, ZA-7945 Cape Town, South Africa
[8] Groote Schuur Hosp, Anzio Rd,Observ, ZA-7945 Cape Town, South Africa