[1] Univ Edinburgh, Usher Inst, NIHR Global Hlth Res Unit Resp Hlth RESPIRE, Edinburgh, Midlothian, Scotland
[2] Univ Putra Malaysia, Fac Med & Hlth Sci, Dept Family Med, Serdang, Malaysia
[3] Univ Malaya, Fac Med, Dept Primary Care Med, Kuala Lumpur, Malaysia
[4] Univ Edinburgh, Ctr Biomed Self & Soc, Usher Inst, Edinburgh, Midlothian, Scotland
[5] Univ Edinburgh, Asthma UK Ctr Appl Res, Usher Inst, Edinburgh, Midlothian, Scotland