[1] Copenhagen Univ Hosp, Herlev Hosp, Clin Biochem, Herlev, Denmark
[2] Copenhagen Univ Hosp, Hvidovre Hosp, Resp Sect, Hvidovre, Denmark
[3] Copenhagen Univ Hosp, Rigshosp, Clin Biochem, Copenhagen, Denmark
[4] Univ Hosp South Manchester NHS Fdn Trust, Manchester Acad Hlth Sci Ctr, Resp Res Grp, Manchester, Lancs, England