[1] Univ Exeter, Coll Med & Hlth, College House,St Lukes Campus,Heavitree Rd, Exeter EX1 2LU, England
[2] Queen Mar y Univ London, Wolfson Inst Populat Hlth, Barts & London Sch Med & Dent, Primar Care Canc Res, London, England
[3] Univ Cambridge, Dept Publ Hlth & Primar Care, Primar Care Unit, Cambridge, England