Conflict of interest: J.A. Whitty reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study. Conflict of interest: J. Rankin reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study. Conflict of interest: D. Visca reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study. Conflict of interest: V. Tsipouri reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study. Conflict of interest: L. Mori reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study. Conflict of interest: L. Spencer reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study. Conflict of interest: H. Adamali has nothing to disclose. Conflict of interest: T.M. Maher has, via his institution, received industry-academic funding from GlaxoSmithKline R and D and UCB, and has received consultancy or speakers fees from Apellis, AstraZeneca, Bayer, Biogen Idec, Boehringer Ingelheim, Galapagos, GlaxoSmithKline R and D, Indalo, Pliant, ProMetic, Roche, Samumed and UCB. Conflict of interest: N.S. Hopkinson reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study. Conflict of interest: S.S. Birring reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study; fees (to Kings College Hospital) for using KBILD from Boehringer Ingleheim, Roche, Galapogos and Novartis, outside the submitted work. Conflict of interest: M. Farquhar reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study. Conflict of interest: A.U. Wells reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study; personal fees for lectures and advisory board work from Boehringer Ingelheim, Roche and Bayer, outside the submitted work. Conflict of interest: P. Sestini reports grants from Research for Patient Benefit Programme National Institute for Health Research (Ref: PB-PG-0712-28073), and Royal Brompton and Harefield NHS Foundation and Trust, during the conduct of the study. Conflict of interest: E.A. Renzoni reports grants from Research for Patient Benefit Programme National Institute for Health Research (ref: PB-PG-0712-28073), during the conduct of the study; personal fees for lectures and advisory board work from Boehringer Ingelheim and Roche, personal fees for lectures from Mundipharma, outside the submitted work.