[1] UCL, Inst Epidemiol & Populat Hlth, Res Dept Primary Care & Populat Hlth, London, England
[2] Univ Sains Islam Malaysia, Fac Med & Hlth Sci, Dept Primary Hlth Care, Nilai, Malaysia
[3] Univ Malaya, Fac Med, Dept Primary Care Med, Kuala Lumpur, Malaysia
[4] Univ Putra Malaysia, Fac Med & Hlth Sci, Dept Pathol, Serdang, Malaysia
[5] UCL, Royal Free Hosp, Inst Epidemiol & Populat Hlth, Res Dept Primary Care & Populat Hlth, Upper Third Floor,Rowland Hill St, London NW3 2PF, England