[1] Univ Nottingham, Dept Epidemiol & Publ Hlth, Nottingham, England
[2] Royal Coll Phys London, Clin Effectiveness & Evaluat Unit, London, England
[3] Nottingham Univ Hosp, Resp Med, Nottingham, England
[4] Nottingham Univ Hosp, Dept Oncol, Nottingham, England
[5] Univ Nottingham, Nottingham, England