[1] Kings Coll London, Dept Med, London, England
[2] Weill Cornell Med Coll, Dept Med, New York, NY 10065 USA
[3] Veteran Affairs Pittsburgh Hlth Care Syst, Pittsburgh, PA USA
[4] Univ Cambridge, Dept Publ Hlth & Primary Care, Cambridge, England
[5] Jama Med Ctr, Dept Med, New York, NY USA
[6] Emory Univ, Rollins Sch Publ Hlth, Hubert Dept Publ Hlth, Atlanta, GA 30322 USA
[7] MedStar Hlth, Baltimore, MD USA
[8] South African Med Res Council, Cape Town, South Africa
[9] Univ Cape Town, ZA-7925 Cape Town, South Africa
[10] George Inst Global Hlth, Sydney, NSW, Australia
[11] Univ Med Ctr Utrecht, Julius Ctr Hlth Sci, Utrecht, Netherlands
[12] Univ Med Ctr Utrecht, Primary Care, Utrecht, Netherlands