1Division of Pulmonology, Dept of Medicine, Stellenbosch University and Tygerberg Academic Hospital, Cape Town, South Africa.
2Groningen Research Institute for Asthma and COPD (GRIAC)
3Univ London Imperial Coll Sci Technol & Med, Imperial College London
4Univ Stellenbosch, Stellenbosch University, Dept Med, Div Pulmonol
5Univ Cape Town, University of Cape Town, Groote Schuur Hosp
6Univ Heidelberg Hosp, Ruprecht Karl University Heidelberg, Pulmonol & Crit Care Med, Thoraxklin