[1] Univ Coll London Hosp, London NW1 8BU, England
[2] UCL, Royal Free & Univ Coll Med Sch, Div Populat Hlth, Res Dept Infect & Populat Hlth, London WC1E 6JB, England
[3] Univ Coll London Hosp, Dept Histopathol, London WC1E 6JJ, England
[4] Univ Coll London Hosp, Dept Imaging, London NW1 8BU, England