[1] Univ Southampton, Southampton Clin Trials Unit, Southampton, Hants, England
[2] Cardiff Univ, Div Populat Med, Cardiff, S Glam, Wales
[3] Univ Southampton, Primary Care & Populat Sci, Southampton, Hants, England
[4] Univ Bristol, Populat Hlth Sci, Bristol, Avon, England
[5] Univ East Anglia, Norwich Med Sch, Hlth Econ Grp, Norwich, Norfolk, England
[6] Univ Nottingham, Ctr Evidence Based Dermatol, Nottingham, England
[7] Univ York, Hull York Med Sch, York, N Yorkshire, England