[1] Kings Coll London, Dept Primary Care & Publ Hlth Sci, Div Hlth & Social Care Res, London SE1 3QD, England
[2] Univ Minnesota, Sch Med, Dept Family Med & Community Hlth, St Paul, MN 55108 USA
[3] Univ Minnesota, Dept Hlth Informat, St Paul, MN 55108 USA
[4] Kings Coll London, Dept Informat, London SE1 3QD, England
[5] Univ Birmingham, Sch Elect Elect & Comp Engn, Birmingham, W Midlands, England
[6] Univ Birmingham, Sch Hlth & Populat Sci, Dept Primary Care Clin Sci, Birmingham, W Midlands, England