Funding for this research was provided by:
RCUK | Medical Research Council (MR/K007017/1)
Received: 12 September 2018
Accepted: 22 June 2019
First Online: 17 July 2019
: A.S. is Editor-in-Chief of <i>npj: Primary Care Respiratory Medicine</i> but was not involved in the editorial review of nor the decision-making process in relation to this article. H.P. is an associate editor of <i>npj: Primary Care Respiratory Medicine</i>. H.P. and A.S. also co-chaired the diagnosis section of the BTS/SIGN Asthma Guideline. The remaining authors declare no competing interests.